Saturday, May 26, 2012

Stocks chill in hot summer

May 26, 2012:  
Investors wilting under the searing summer heat wave were further tormented by a steep petrol price hike last week. But this hike helped rein in the unfettered fall in the rupee. The India currency was threatening to spin below 56 against the dollar. Stock prices also recovered after the fuel price hike though the Sensex continued its jig around the 16,000 mark, keeping investors edgy.
Euro zone and its troubles continued to affect global financial markets. Worries over the health of Spanish banks and Greece' possible exit from the euro zone kept stock prices on a leash. Euro zone's PMI declining to 45.9 in May, down from 46.7 in April further roiled the sentiment in this region.
Cash volumes were very low last week. Action in derivatives picked up towards the weekend. FIIs were selling small quantities through the week. But the net FII outflow in May is at a very low level of $97 million. Open interest moved slightly higher above 1,30,000 crore. But low put-call ratio implies that the market is getting oversold at these levels.
The rupee's rout appears to have halted and that can provide temporary relief to stock prices next week. Expiry on May contracts can usher in some volatility. It would be good to bid adieu to May, a month that is known for its negative effect on the stock markets.
It could be good time to bring out your shopping list since the Sensex is approaching its long-term base around 15,000. Cherry picking is advised only when market is at its gloomiest best.
Oscillators in the daily chart reflect the change in the downward momentum. Rate of change oscillator in the daily chart is reversing higher from bearish zone. It is on the verge of moving in to the positive territory. Daily relative strength index is also attempting to move up from the oversold zone. Momentum indicators in weekly chart dipped in to bearish zone but they are moving sideways instead of moving any deeper in this territory.
The Sensex (16,217.8) is displaying resilience above the critical 16,000 level. We stay with the targets of 16,016 and then 15,080 for the current decline from 18,523 peak. As explained earlier, the index could form a higher bottom around 16,000. But if this level is breached, the index could form a low around 15,000. Many wave targets and supports also converge at this level making it a good point from where the Sensex can rebound.
Short-term resistances for the Sensex would be at 16,466, 16,670 or 16,872. Short-term view will turn positive only on a close above 16,872.
The presence of the 200-day moving average in that region makes it a very significant hurdle.
The halt last week appears to be a temporary pause. If rallies next week have trouble moving past 16,500 it will mean that there can be another decline to 15,725, 15,329 or 14873 before the index stabilises.
Nifty (4,921.4)
The Nifty did not slide further last week but there was no rebound either. The wave sequence that began from the 5,630 peak could still be evolving. Key hurdles for the Nifty next week would be at 5,000, 5,093 and 5,130.
Short-term traders can initiate fresh shorts if the index is unable to move beyond 5,000. That would mean that the index will decline to 4,757, 4,634 or 4,493 in the near term. Short-term view will turn positive only on a close above 5,130. The 200-day moving average positioned at 5,080 will also pose strong obstacle in the upcoming weeks.
Medium-term trend in the Nifty remains down and we stay with the medium-term targets of 4,884 and 4,600. Since the index is close to the first target, short sellers should watch out for sudden rebound from these levels.
Global Cues
Global markets halted their steep slide and etched minor gains last week. Greece continued to cast its shadow on the global market and cappedany significant up-move. CBOE volatility index declined slightly to end the week at 21.7, indicating that investor trepidation did not rise any further.
The Dow recovered from the intra-week low at 12,311. We stay with the view that the medium-term uptrend in the index will be threatened only on a strong close below 12,000. The key support from a long-term perspective is at 10,500. If the Dow manages to move beyond 12,700, it will denote that the index can move beyond 13,300 again in the upcoming weeks.
The dollar index gained against all major currencies including the euro. This resulted in the dollar index shooting higher to 82.6 last week. Key medium-term resistance for this index is, just above at 82.7.
If this level is crossed, the greenback can shoot higher against most other currencies, causing further deterioration in rupee value. Strength in dollar is resulting in gold moving lower. Comex gold has come close to its key support at $1,566. This level has supported gold in September 2011 and again in December 2011. Key long-term support for this metal is at $1,446.

Questions for Pro-Engineer


Q 1 What is the maximum number of characters allowed in a Pro/ENGINEER object name?
Thirty one (31) characters can be used in Pro/ENGINEER object names. This number does not include the extension, i.e., .prt, .asm, .drw, or the object version number, i.e., .1, .2, .3.

Q2 .Can upper case characters be used in Pro/ENGINEER object names?

Upper case characters cannot be specified in Pro/ENGINEER object file names. Upper case characters can be specified during object creation, however, the file will be written to disk using lower case characters only.

Q.3 what is the reason for using a config.pro file?
The config.pro file is used to control the environment in which Pro/ENGINEER runs. There are over 150 available options which allow control of a variety of different aspects, ranging from model display to default units to search paths used to retrieve assembly components.

Q.4 is a default config.pro file created when Pro/ENGINEER is installed?
When Pro/ENGINEER is initially installed, there is no default config.pro file that is created automatically. However, a large number of the options do have default values which are used unless the option setting is changed in a config.pro file. The Configuration Options section of Pro/HELP lists the default config.pro option values in italics. There are two methods that can be used to create a config.pro file. The first method is to utilize any text editor, vi for example, and manually create the file. Each option should have its own line in the file, with the format being {Option Value}. The second method is to use the Preferences dialog box within Pro/ENGINEER, which can be accessed by selecting Utilities, Preferences... When you exit the dialog box, the config.pro file will be written to your local directory. See the Suggested Technique for Using the Preferences Dialog Box for a detailed description of the functionality for this new dialog.

Q.5 Where does Pro/ENGINEER look for config.pro files?
Pro/ENGINEER looks for config.pro files in 3 different directories in the following order:
1) load point/text
Config.pro files residing in load point/text will be read first.
2) The user's home directory
With UNIX systems, Pro/ENGINEER will read the config.pro file in the user's home directory. This is most commonly used for specifying user customized config.pro options such as colors and mapkeys.
3) Working directory
The directory in which Pro/ENGINEER starts is searched for a config.pro file.
If the same option appears in more than one config.pro file, the one that was read last will be utilized by the system.

Q.6 After config.pro is edited, why aren't the changes reflected?
After config.pro is edited, the Add/Change and Apply buttons must be selected in the Preferences dialog box in order for the modifications to be reflected in the Pro/ENGINEER session, or Pro/ENGINEER can be restarted. Be aware that some config.pro options require Pro/ENGINEER to be restarted in order for config.pro modifications to be reflected.

Q.7 After config.pro is edited, is it necessary to restart Pro/ENGINEER?
After config.pro is edited, the Apply button must be selected in the Preferences dialog in order for the modifications to be reflected in the Pro/ENGINEER session, or Pro/ENGINEER can be restarted. Modifications to the following config.pro options require Pro/ENGINEER to be restarted.

Q.8 what is the difference between config.pro and config.sup?
There are two main differences between config.pro and config.sup.
Unlike config.pro, config.sup can only be located in the load point/text directory.
Config.sup options cannot be overridden by options found in any other config.pro. Also, items contained in the config.sup can only have one entry per option. Keeping this in mind, it is important that items which can have multiple entries, such as "mapkey", "search path", and "def_layer" are not specified in config.sup.

Q.9 Is there a limitation on the number of characters that can be included in a config.pro entry?
Ans: Each line in config.pro is limited to 80 characters. Environment variables can be used to specify config.pro "search_path" values containing more than 80 characters. Refer to Configuration Options in Pro/HELP for details.

Q.10 Where are Pro/ENGINEER objects stored when File, Save is selected?
By default, Pro/ENGINEER objects will be stored to the current working directory. If the working directory is changed using File, Working Directory, Pro/ENGINEER objects will be saved to the new directory. If a Pro/ENGINEER object is retrieved from a directory other than the current working directory, Pro/ENGINEER will save the object back to the directory from which it was retrieved. If the user does not have write permission in that directory, the object will not be saved unless the config.pro option "save_object_in_current" is set to "yes".

Q.11 What does File Save As do?
File - Save As will make a copy of a specified Pro/ENGINEER object using a new name. List the object that is to be copied in the Model Name space in the Save As dialog box, the current object being the default. In the New Name space, a new file name should be specified. Pro/ENGINEER will create this object in the current working directory.

Q.12. what does File, Backup do?
File, Backup can be used to save Pro/ENGINEER objects to a specified directory. The object will be saved in the specified directory using the original filename(s).
File, Backup in Assembly, Drawing, or Manufacturing modes will save all related objects to the specified directory.

Q13 what does File, Rename do?
File, Rename is used to change the name of Pro/ENGINEER objects in memory and on disk. Pro/ENGINEER will rename all versions of the object being renamed.
When renaming an object that was retrieved from directory other than the current working directory, the renamed object will be saved in the directory from which the object was retrieved.

Q14 what does File, Erase, Current do?
File, Erase is used to clear the specified object from workstation memory. This functionality will not remove objects from disk. Objects referenced by an active assembly or drawing can not be erased. A list of objects in the current model will then be displayed. Only the current top level model (i.e. assembly or drawing) can be erased, and selected objects as well.

Q15 what does File, Erase, Not Displayed do?
Ans: File, Erase, Not Displayed is used to erase all objects from the current session, except for those that are currently displayed and any objects referenced by the displayed objects. For example, if an assembly instance is being displayed at the time Erase, Not Displayed is selected, the instance, the instance's generic, and it's components will not be erased. There is a config.pro option related to File, Erase, Not Displayed called "prompt_on_erasenotdisp".
yes (default) - a message window for each eligible object in question appears, asking if you want to first save the object before it is erased.
no - the system will immediately erase all eligible objects.

Q 16 What does File, Instance Operations do?
File, Instance Operations will save a particular instance of a part or assembly in a separate file called an " instance accelerator file" (suffix ".xpr" for a part, ".xas" for an assembly). This file is used to retrieve particular instances quickly from disk rather than having to first retrieve the generic into memory, selecting the particular instance according to the family table, and then regenerating. Therefore, with this functionality the amount of time that it takes to retrieve an instance of a part or assembly from disk can be considerably reduced. The trade off is that more disk space will be used to store the accelerator files. When File, Instance Operations is selected, the INST DBMS menu appears with the following options
InstIndex - create or update the Instance Index file for a specified directory
pdate Accel - create or update accelerator files for all instances currently in session
Purge Accel - examine each instance accelerator file and delete it if it is not current with
SaveAccelEnv - brings up the SV INST ACC menu When SaveAccelEnv is selected the SV INST ACC menu appears with the following options:
none (default) - the system does not save the instance in a file separate from the model.
always - the system always saves the instance in a separate file
explicit - the system saves the instance in a separate file only. When the instance is explicitly saved.
The config.pro option "save_instance_accelerator" can also be used to control instance accelerator files. The values for this config.pro option are also none (default), always, explicit. When you bring up the SV INST ACC menu, one of the options will be highlighted to reflect the last setting. That setting could have been either loaded from a configuration file or selected previously from this menu.

Q 17 Does Pro/ENGINEER over write existing objects when saving to disk? What does the object version number indicate?
Ans: Pro/ENGINEER will not overwrite existing objects while saving to disk. Objects are saved to disk with an object version number after the file extension. Pro/ENGINEER will create a new object file each time the object is saved, monotonically increasing the version number each time.
The object version number indicates the number of times the object has been stored. Objects are saved to disk with an object version number after the file extension. Example: A part called valve.prt will be initially written to disk as valve.prt.1. Subsequent storage of this object will result in the files valve.prt.2. valve.prt.3, etc. If the directory is purged, the object with the highest version will remain.
When a top-level object is retrieved (for example, an assembly drawing), it always retrieves the most recent version of the assembly and its parts. Therefore, the version of the drawing does not necessarily have to have the same version number as the part or assembly. This will frequently be the case when several different users are working on the same files.
This wouldn't cause a problem unless a user deletes or redefines a feature that is used as a reference by some other object. For example, if a feature is deleted from a part that is used for assembling another component in an assembly, then that component will fail placement when the assembly is retrieved, and must be redefined. Another example is when planar surfaces are used to orient the model in a drawing view, and the feature is then deleted or suppressed. This will result in the message, "model geometry for drawing view is missing", and the view will revert to an isometric orientation, and must be re-oriented (using the default datum planes to orient the views whenever possible will help to prevent this).
The best method for avoiding these situations is to use a database management product that will manage revision changes made to parts/assemblies/drawings. Without a system like this, any user can change any model, regardless of what other users are doing.

Q 18 Does Pro/ENGINEER offer an auto-save function?
Auto-save functionality is not currently implemented in Pro/ENGINEER. The "prompt_on_exit" config.pro option can be utilized to prompt the user to save objects in session before exiting Pro/ENGINEER.

Q 19 What happens if I run out of disk space while saving my objects?
If available disk space is depleted during storage, Pro/ENGINEER will issue the message: object name could not be saved: Check disk space or write access. Error in storage. Check previous message (then press Enter):"Pro/ENGINEER will not save any portion of the object to disk. Disk space must be made available before the object can be saved.

Q 20 What is the difference between File, Erase and File, Delete?
File, Erase removes the object from workstation memory. The object is not removed from disk. File, Delete removes either old versions or all versions of the object and all associated objects from disk. It is recommended to approach this menu selection with a great deal of caution. Creating backup copies of Pro/ENGINEER objects is considered good practice and can reduce the effect of accidental removal of data.

Q 22 Why is the following message given: "PDM database object must be renamed by Pro/PDM application"?
By default, Pro/ENGINEER will not allow Pro/PDM objects to be renamed within Pro/ENGINEER. The config.pro option "let_proe_rename_pdm_objects" set to "yes" will allow Pro/ENGINEER to rename Pro/PDM objects.
Warning: Objects renamed in Pro/ENGINEER will be considered new Pro/PDM objects when submitted back to a Pro/PDM database.

Q 23 Why aren't part files saved when File, Save is selected in Sketcher?
While in Sketcher, the File, Save functionality will save the section to disk rather than the part file. This functionality allows sections to be stored to disk for future use in feature creation. Section files are saved to disk with a .sec file extension. Once Sketcher is exited by either completing the feature creation or quitting, File, Save will save the part file to disk.

Q 24 How is family table instances stored to disk?
All family table instance information is stored within the generic model.Pro/ENGINEER does not save a unique object file to disk for each instance.
Q 25 How can copies of a part be created?

Ans : The File, Save As functionality allows copies of part files to be created using the following technique: Select File, Save As. Pro/ENGINEER will open a Save As dialog box. The current object in memory will be the default object to copy (in the Model Name section of the dialog). The name of the new object is specified in the New Name line in the dialog.

Q 26 Does Pro/ENGINEER save all components each time an assembly is saved?
Ans : By default, Pro/ENGINEER does not store all assembly components to disk upon each File, Save operation. Instead, Pro/ENGINEER will save the assembly file and only components that have been modified. By setting the config.pro option "save_objects", this can be changed. By using this option, Pro/ENGINEER can be instructed to save all dependent objects, save only the objects that were modified, or save modified objects and objects specified by the user.

Q 27 Where does Pro/ENGINEER save part files that are assembled from a directory different than the current working directory?
Ans : By default, Pro/ENGINEER will store objects that are assembled from other directories back to the directory of origin. If the user does not have write access to the directory, Pro/ENGINEER will not store the objects in the current working directory, unless specific config.pro options have been set. The config.pro options "override_store_back" and "save_object_in_current" allow greater control over this type of situation.

Q 27 What happens during storage of an assembly if its dependent part files are located in a write-protected directory?
Ans : By default, Pro/ENGINEER will only store modified objects and will always store objects back to the directory from which they were retrieved. Therefore, if a part from a write protected directory has been modified and File, Save is selected, Pro/ENGINEER will not be able to save the object unless the config.pro options "override_store_back" and "save_object_in_current" are utilized.

Q 28 Why can't an assembly be retrieved after clearing it from memory or after starting a new session of Pro/ENGINEER?
During assembly creation, it is possible to add components to the assembly that are located in directories other than the current working directory. When the assembly is saved, the assembly file is saved to the current working directory while modified components are saved back to the directories of origin. If the assembly is cleared from workstation memory by either exiting Pro/ENGINEER or by selecting File, Erase, and selecting all the objects in the ERASE dialog box and then retrieved, it is possible that Pro/ENGINEER will not be able to locate certain components. The config.pro option "search_path" can be used to specify directories which Pro/ENGINEER will search for objects. The config.pro file must contain a separate "search_path" option for each directory to be searched. Refer to the Configuration Options section of the Pro/HELP for details.

Q 29 How does File, Save As function in Assembly mode?
In Assembly mode, the File, Save As functionality allows any or all members of the assembly to be copied.
By default, after selecting File, Save As, a dialog box will appear with the name of the assembly to be copied specified next to Model Name. The new assembly name is specified on the next line (New Name). After selecting OK, a check mark can then be placed next to each assembly component to be copied or Include all subcomponents can be selected to copy all assembly components.
If a check mark is placed next to any of the components or if Include all subcomponents is selected, Pro/TABLE will be displayed where new component names can be specified in the cell adjacent to the original.
If OK is selected without selecting a component or Include all subcomponents, Pro/ENGINEER will create only a copy of the assembly which references the original components.
The config.pro option "model_rename_template" is used to create a user defined renaming scheme.
Refer to the Configuration Options section of the Pro/HELP for further information.

Q 30 Why do parts intersected by assembly features require renaming before they can be stored?
Ans : Assembly features which intersect assembly components alter the geometrical intent of the original object. When the assembly is in session, the component exists in memory in two different states. When Pro/ENGINEER tries to save the assembly, it is unclear which state of the component is to be saved. Pro/ENGINEER will prompt the user to save the object with a new name. This will create a copy of the object containing the geometric result of the assembly feature.

Q 31 What does the config.pro option "override_store_back" do?
If the config.pro option "override_store_back" is set to "yes", Pro/ENGINEER will save objects retrieved from other directories to the current working directory;
If "override_store_back" is set to "no", which is the default, objects will be saved in the directory of origin. If the option is set to "no" and the user does not have write access to the directory of origin, Pro/ENGINEER utilizes the config.pro option "save_object_in_current".

Q 32 What does the config.pro option "save_object_in_current" do?
When the config.pro option "save_object_in_current" is set to "yes", Pro/ENGINEER will save objects to the current working directory if the user does not have write access to the directory from which the object was originally retrieved. If the option is set to "no", Pro/ENGINEER will not save the object at all. This option should be used in conjunction with the config.pro option "override_store_back".

Q 33 What is the preferred method to make a copy of an assembly?
The File, Save As functionality is the best way of copying assemblies.

Q 34 What is the preferred method to rename assembly components?
The following procedure should be used to rename assembly components:
Retrieve the assembly which contains the components to be renamed
In a sub-window retrieve the component to be renamed
With the component active, select File, Rename and enter the new component name
Select Window, Activate and pick in the window containing the assembly
Regenerate the assembly
Select File, Save to save the assembly which contains a reference to the new component name.

Q35 what is the preferred method to rename a drawing?
The File, Rename functionality should be utilized to rename a drawing.

Q36 What is the preferred method to copy a drawing and its model?
The following procedure should be used to create a copy of a Pro/ENGINEER drawing:
Select File, Save As, which will bring up a Save As dialog box
Enter the name of the drawing to copy, the current drawing is specified by default
Enter the new drawing name, and select OK.
The following procedure can be used to create a copy of a drawing and copy of the drawing model:
Create a new directory
Select File, Backup from the drawing window, and specify the new directory as the destination. Pro/ENGINEER will create a copy the drawing and the model
Select File, Erase and clear the current drawing and model from memory
Select File, Working Directory select the new directory as the current working directory
Retrieve the backup drawing
Select File, Open and retrieve the part to be copied in a sub-window
With the part active, select File, Rename and rename the part
Select Window, Activate and pick in the window containing the drawing
Regenerate, rename if necessary (selecting File, Rename) and save the drawing.
The following procedure can be used to create a copy of a drawing and a copy of the drawing model, ONLY IF both the model and the drawing have the same name (i.e.. valve.prt and valve.drw):
Set the config.pro option "rename_drawings_with_object" to "both"
Retrieve the model and have the drawing either in session or in the current working directory
Select File, Save As on the model
Enter the new model name in the New Name field in the Save To dialog box.
And a message will appear in the Message Window saying that the Drawing and the Part were copied to the new name.
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View Functions
General:
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*How can the orientation of the default view be changed?
The default model orientation can be redefined by setting the config.pro options "x_angle" and "y_angle" to the desired values of the rotation, in degrees, of the object about the x and y axis. In addition, the model can be saved in user defined orientations by selecting View, Saved Views, entering a unique view name, and then Save. The model can easily be reoriented into the saved view orientation by selecting View, Saved Views, selecting the saved view name and then Set.

Shading:
*How can the quality of a shaded model be increased?
The quality of the shaded model can be increased be selecting View, Model Display, Shade. Specify the shade quality between 1 and 10; the number 3 is the default. Increasing the shade quality to higher values may result in an increase in shading time. In addition, Small surfaces may be check marked in order to shade very small surfaces, such as round features, which otherwise may not be shaded unless the model is zoomed in.
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*When a shaded model is spun, why does it revert back to wireframe?
Pro/ENGINEER shaded models will revert to wireframe if the machine is not configured for hardware shading capabilities. In order to have the model remain shaded during a spin operation, the workstation must have an appropriate graphics card installed, and the "graphics" option in the config.pro file must be set based on the type of workstation being used. Refer to the Hardware Configuration Notes on www.ptc.com for specific details.
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*How can a postscript file of a shaded model be created?
To create an encapsulated postscript (EPS) file of a shaded model select File, Export, Image, change the type to EPS, and then OK. Select Dimensions Size, or Resolution DPI or Image Depth for additional options and finish by selecting OK.
Refer to the Hardware Configuration Notes on www.ptc.com for details on EPS plotter support.
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*Why aren't surface features displayed when the model is shaded?
When the config.pro option "shade_surface_feat" is set to "no", surface features will not be displayed when the model is shaded.
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Colors:
*How is a color map file stored to disk?
A user defined color map can be stored to disk by selecting View, Model Setup, Color Appearances, File, Save As, and enter the name color.map in the New Name field in the Save As dialog box. Pro/ENGINEER will create a file called color.map in the current working directory.
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*Where does the color.map file need to be located in order for Pro/ENGINEER to recognize it?
The color map file, color.map, will be automatically loaded if it is located in the directory that Pro/ENGINEER is executed from. The configuration file option "pro_colormap_path" can be used to specify the location of a color map file that is not located in the startup directory.
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*How many different colors can be defined and stored to the color.map file?
The exact number of colors that can be defined will vary, depending on the type of workstation and the graphics card that is being used. Higher end graphics cards will typically allow a greater number of colors to be defined.
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*Why is the Transparency menu selection not available?
The transparency functionality is offered only with hardware graphics configurations. Refer to the Hardware Configuration Notes for other items available with hardware graphics configurations.
On machines configured to use hardware graphics, the transparency functionality must be enabled by selecting View, Model Display, Shade, and Enable the Transparency option.
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*When a color is assigned to a part in Assembly mode, why is the color not reflected in Part mode?
Colors assigned to parts in Assembly mode do not effect Part mode. This functionality allows assembly colors to represent a production operation done after assembling the individual parts, e.g., the application of paint.
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*In Assembly mode, why does the part display with a different color than what was defined in Part mode?
Colors applied to components in Assembly mode will override colors defined at the Part level. To unset an assembly color, retrieve the assembly and select View, Model Setup, Color Appearances, Component, select the component in question and then Unset.
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Exploded Views:
*Why does a subassembly explode when the top-level assembly is exploded?
By default, subassemblies explode when the top-level assembly is exploded. The top-level assembly can be modified to specify which subassemblies and which parts within the subassembly to explode by selecting Modify, Mod Expld, Expld Status. Select Toggle Expld from the EXPLD STATUS menu and pick the components in the Model Tree that are not to be exploded (changing the value to Unexploded).
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*How can exploded views show the axes of the explosion?
This functionality is not currently implemented in Pro/ENGINEER. However, datum axes can be created using one of several available methods. The type of datum axis to use will depend on the specific situation.
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*How can an exploded view be saved to a named view?
Exploded views can be saved to a name by exploding the assembly, then selecting View, Saved Views, and then Save a new name. When an exploded view name is retrieved, the assembly can be unexploded using View, Unexplode.
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Misc Operations
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*What is the File, Working Directory menu selection used for?
The File, Working Directory menu selection allows the Pro/ENGINEER working directory to be changed. After selecting Working Directory, Pro/ENGINEER allows navigation through the directory tree structure.
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*What is the Window, Open System menu selection used for?
When Window, Open System is selected, Pro/ENGINEER will execute a system shell. The current working directory for this shell is the Pro/ENGINEER working directory. The Pro/ENGINEER session will be suspended while the system window is active. Exiting out of the system window will allow the Pro/ENGINEER session to continue.
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*Why do the Pro/ENGINEER windows become inaccessible after Window, Open System is selected?
The Pro/ENGINEER session will be suspended while the system window is active. Exiting out of the system window will allow the Pro/ENGINEER session to continue.
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*What is the Help, Customer Services Info menu selection used for?
The Help, Customer Services Info menu selection will open a Pro/ENGINEER information window giving the active Pro/ENGINEER config ID number, the Revision and build of Pro/ENGINEER, and almost all information about your system's configuration. This information is specific to your site and used by Parametric Technology Technical Support as a means of determining your software configuration and licensing.
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*What else does the Help, Customer Services Info menu selection provide?
The Help, Customer Services Info menu selection will open a Pro/ENGINEER information window providing the following information:
Licensing Information - Software Version
- Configuration Id
- Pro/ENGINEER loadpoint directory
- License Configuration (Locked or Floating)
- All included Pro/ENGINEER options
Machine Information - Hostname - Username - CPU id - Pro/ENGINEER machine type - OS name, release, and version - Pro/ENGINEER graphics type
Installation Directories and Command Information
Configuration Information - Configuration files read
Auxiliary Application Information (includes floating option information if available)
Parametric Technology Information - Important phone and fax numbers - WWW home page address - Internet e-mail address - technical support address
This information is specific to your site and used by Parametric Technology Technical Support as a means of determining your software configuration and licensing. This information is written to a support.inf file in the current working directory of Pro/ENGINEER.
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*What is the Utilities, Mapkey menu selection used for ?
The Utilities, Mapkey menu selection is used to create a mapkey by recording a series of menu picks and assigning these picks to a keyboard key or keys. The created mapkey can be stored in the config.pro file for use in other sessions of Pro/ENGINEER or be specified to be used in the current session only.
When Utilities, Mapkey is selected the Mapkey dialog box appears with the following options.
New - Create a new mapkey and starting recording picks.
Modify - Modify the highlighted mapkey.
Run - Execute the highlighted mapkey.
Delete - Delete the highlighted mapkey.
Save - Save the current mapkeys to a config.pro file.
See the Suggested Technique for Creating Mapkeys using the Mapkey Functionality for more information on the Mapkey functionality.
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*In which directory does Pro/ENGINEER create trail files?
Each time Pro/ENGINEER is executed, a trail file is created called trail.txt.n; where n represents the file version number which monotonically increases with each new file. By default, Pro/ENGINEER trail files are written to the current working directory. The config.pro option "trail_dir" can be used to specify a directory to which the Pro/ENGINEER trail files are to be written.
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*Why is Pro/ENGINEER unable to execute a trail file with the file name "trail.txt"?
Pro/ENGINEER does not allow trail files to be executed having the file name "trail.txt". The file must be renamed since Pro/ENGINEER creates a new file "trail.txt" each time the software is executed. Trail files must be in the format filename.txt; where filename represents a string other than "trail".
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*What would cause a trail file to go out of sequence?
There are many possibilities that would lead to a trail file going out of sequence. Before executing the trail file, the Pro/ENGINEER environment must be exactly the same as it was during initial creation of the trail file. For example, if the trail file retrieves a part and makes modifications to it, the same version of the part must reside in the same location as it was found initially. In addition, the same config.pro options must be utilized. If, for example, the display of datum planes was modified, this could cause an out of sequence error. If a trail file does go out of sequence, the user will be notified of the line number that could not be executed. To troubleshoot this type of problem, copy the original trail file to a backup name, then edit the original trail file by removing all the lines after the one that caused the out of sequence error. Also remove five to seven lines before the point of failure. At this point, rerun the edited trail file, then manually walk through the menu selections by viewing the backup trail file. By doing this, it will be clear what is causing the problem.
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*Is there a way to force the trail file to stop after each menu pick?
With the config.pro option "set_trail_single_step" set to "yes", a trail file will stop after each trail file step. Entering a carriage return will allow the trail file to proceed.
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*Is there a way to force the trail file to pause after each menu pick?
The config.pro option "trail_delay" will force a trail file to pause for a specified number of seconds between trail file steps. The value for the "trail_delay" option is the delay period specified in seconds.
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Q How can the size of the Pro/ENGINEER working window be controlled?
The default size of the Pro/ENGINEER working window can be controlled using the config.pro option "windows_scale". The window scaling factor is specified as the value to the "windows_scale" option ranging from 0.5 to 1.0. The default value for the "windows_scale" option is 1.0.
Pro/ENGINEER must be restarted in order for modifications to the value of "windows_scale" to appear.
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*How can the fonts used in the Pro/ENGINEER menus be changed?
There are several config.pro options that can be used to change the Pro/ENGINEER menu fonts.
The configuration file option "default_font" option is used to change the font used by Pro/ENGINEER for items other than the menu bar, menus and their children, and pop-up menus. For Unix machines, this must be the name of a font available at the X-server running Pro/ENGINEER. The "xlsfonts" command can be used to list available system fonts. The standard default font for Unix systems is helvetica, regular,12. The standard fonts for Windows NT and Windows 95 are inherited from the system settings made with the Control Panel. The "default_font" format should be:
default_font name, style, point_size
Spaces are acceptable and the values may be in any order. Example:
default_font courier, italic, 12
In addition, the configuration file options "menu_font" and "popuphelp_font" can be used to separately control the font of the menus and pop-up screens. Pro/ENGINEER must be restarted in order for these modifications to appear.
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*How can the default location of the Pro/ENGINEER working window be changed?
Pro/ENGINEER does not currently allow the default location of the Pro/ENGINEER working window to be redefined, however the scale of the working window can be modified using the config.pro option "windows_scale".
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*Is it possible to prevent the second column of menus from overlapping the Pro/ENGINEER working window?
With the config.pro option "menu_horizontal_hint" set to "right", Pro/ENGINEER will place the second column of menus to the right of the primary menus i.e. the ENVIRONMENT menu will appear to the right of the MAIN menu instead of overlapping the Pro/ENGINEER working window. Be aware that the working window may require a scaling factor using the config.pro option "windows_scale" to provide ample screen space for the secondary menus to be displayed.

Pro/ENGINEER must be restarted in order for modifications to the value of "menu_horizontal_hint" to appear.
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*How can a separate icon be made of each individual working window rather than iconifying the entire Pro/ENGINEER session?
With the config.pro option "iconify_entire_pro" set to "no", individual working windows can be iconified. The default value for "iconify_entire_pro" is "yes".
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Mapkeys
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*What would cause a mapkey to not work properly when it is executed?
The mapkey functionality allows a series of Pro/ENGINEER menu selections and keyboard input to be executed by a keyboard command. If a mapkey will not execute properly, check the following:
If the mapkey was defined during a session of Pro/ENGINEER, verify that the config.pro file has been loaded into the Pro/ENGINEER session using Utilities, Preferences...
Verify that the mapkey syntax has been specified correctly in config.pro.
Verify that the first menu selection defined in the mapkey is displayed in an active Pro/ENGINEER menu.
Verify that each Pro/ENGINEER menu selection that the mapkey is calling is not "grayed out". In other words, a mapkey will fail if a menu selection can not be interactively picked with the mouse pointer.
Verify that the definition of the mapkey in config.pro does not exceed 80 characters. It if does, continue it to the next line using a "\" at the end and then continue the definition on the next line.
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*Where is the mapkey functionality documented?
The mapkey functionality is documented in the Pro/HELP Online Documentation, under the topic To Define Your Own Mapkeys.
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*Is there a limitation in the number of characters that can be included in a mapkey?
All lines in config.pro are limited to 80 characters. Mapkeys containing many characters may be nested together to define a single operation:
Refer to the Pro/HELP Online documentation for further information.
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*How can a mapkey be defined to turn datums on and off?
The display of datum planes is a toggle function in Pro/ENGINEER. One mapkey is used to toggle the display:
MAPKEY dtm #ENVIRONMENT; #Disp DtmPl
Or, as of Release 20, there is a Toolbar icon which can be unselected for each of the datum features.
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*Why are mapkeys not recognized in the config.sup file?
Only the first mapkey defined in config.sup will be recognized in Pro/ENGINEER, per the definition of config.sup.
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*Can keyboard function keys be used in a mapkey?
Function keys may be used for mapkeys and should be defined as follows:
MAPKEY $F2 #FEATURE, #CREATE, #COSMETIC, #SKETCH, #NO XHATCH, #DONE
The "$" sign tells Pro/ENGINEER that F2 is the function key "F2" and not the alpha-numeric characters "F" "2". For NT machines, F10 is predefined as an NT utility and cannot be defined for a mapkey. For more information refer to the Pro/HELP Online Documentation.
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*How can a mapkey call another mapkey?
A mapkey may execute another mapkey. This is called nesting mapkeys:
MAPKEY param #set up; #parameters;
MAPKEY string %param; #part; #create; #string;
This example has the first mapkey "param" making the menu selections to shade the model. The second mapkey "string"
executes the first mapkey "param", defined by %param, and then creates a string parameter. For more information refer to the Pro/HELP Online Documentation.
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*How can keyboard input be included in a mapkey?
Keyboard input can be entered during the execution of a mapkey by selecting Pause for Keyboard Input during the mapkey creation. Then, when making the menu selections that will be included in the mapkey, Pause must be selected to allow the mapkey to stop, so that keyboard input may be entered. For example, to create a mapkey that will automatically create a new part, with a user-defined name, consisting of a default set of datum planes, refer to the Suggested Technique for Creating Mapkeys using the Mapkey Functionality . In this case, the mapkey would pause and wait for the user to input the name of the model, then continue on after the user presses the Resume button to create the default datum planes.
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*Can a mapkey prompt for a screen pick, then continue?
A mapkey may prompt for a screen pick, however it cannot continue once the selection has been made. An alternative technique is to define a second mapkey which will continue once the screen selection has been made.
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Customizing menus using menu_def.pro
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*Where is there detailed documentation on the menu_def.pro file?
Detailed documentation can be located in the Suggested Technique for Customizing Pro/ENGINEER menus using menu_def.pro .
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*Where does Pro/ENGINEER look for menu_def.pro files?
Similar to config.pro, menu_def.pro file can reside in any of 3 directories.
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*How can a menu pick be removed from a menu?
The default Pro/ENGINEER menu selections may not be modified or removed.
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*Why doesn't a menu_def.pro menu selection work when it is picked?
If the added menu selection aborts prematurely, check the following:

If the menu_def.pro file was created within the Pro/ENGINEER session, Pro/ENGINEER must be restarted in order for the modification to be recognized.
Verify that the menu syntax has been specified correctly in menu_def.pro.
Verify that the first menu selection defined in menu_def.pro is displayed in an active Pro/ENGINEER menu.
Verify that the each Pro/ENGINEER menu selection that added menu selection is calling is not "grayed out", in other words, an added menu selection will fail if a menu selection can not be interactively picked with the mouse pointer.
Verify that the definition of the menu selection in menu_def.pro does not exceed 80 characters.
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*How can a new menu selection be placed at the top of a menu?
All menu_def.pro menu additions will be displayed in the bottom of the target menu.
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*How can menu_def.pro be used to create a new menu?
A menu_def.pro will not allow a new menu to be created. Only new menu selections can be added to existing menus.
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Family Tables
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*How can the names of family table items (features, dimensions) be changed so that the names that appear in the column headings are more descriptive?
To change the name of a feature, select Set Up, Name, Feature, select the feature, then enter the new name for the feature. To modify dimensions, select Modify, Dim Cosmetics, Symbol, then enter in the symbol to replace the dimension symbol, "d#".
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*Is there a limit to the number of rows and/or columns that can be included in a family table?
There is no limit to the number of rows and/or columns that can be included in a family table. The size of the dialog box may have to be expanded, in order to see a large number of rows and/or columns at one time.
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*How can negative dimension values be entered in a family table?
In order to enter negative values, the dimension symbol must be preceded by a "$" sign when added to the family table.
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*What does it mean to have nested instances?
Nested instances refer to instances created within other instances.
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*What are .ptd and .idx files? Can they be deleted?
A .ptd file is a text file containing all the information found in the family table, including all instance names and their current values. The .ptd file is created by selecting File, Export Table, and selecting Pro/TABLE as the type of file to export. This file is not required for part retrieval and can be deleted. However, the .ptd file can be used to edit the family table outside of Pro/ENGINEER. If an instance is deleted by modifying the .ptd file, subsequent retrieval of the generic will ask the user if he or she wishes to clean up the family table, at which point any modifications made to the .ptd file will be reflected in the internal family table. In addition, as soon as the generic is stored, the internally stored family table.

Monday, May 14, 2012

Electronic Measurements & Instrumentation

Electronic Measurements & Instrumentation Question & Answers
GRIET/ECE 1
UNIT-1
1. What are the basic performance characteristics of a system?
Ans:
STATIC CHARACTE RISTICS
The static characteristics of an instrument are, in general, considered for instruments which are used to
measure an unvarying process condition. All the static performance characteristics are obtained by one
form or another of a process called calibration. There are a number of related definitions (or
characteristics), which are described below, such as accuracy% precision, repeatability, resolution,
errors, sensitivity, etc.
l. Instrument: A device or mechanism used to determine the present value of the quantity under
measurement.
2. Measurement: The process of determining the amount, degree, or capacity by comparison (direct or
indirect) with the accepted standards of the system units being used.
3. Accuracy: The degree of exactness (closeness) of a measurement compared to the expected (desired)
value.
4. Resolution: The smallest change in a measured variable to which an instrument will respond.
5. Precision: A measure of the consistency or repeatability of measurements, i.e. successive readings
does not differ. (Precision is the consistency of the instrument output for a given value of input).
6. Expected value: The design value, i.e. the most probable value that calculations indicate one should
expect to measure.
7 Error: The deviation of the true value from the desired value.
8. Sensitivity: The ratio of the change in output (response) of the instrument to a change of input or
measured variable.
DYNAMIC CHARACTERISTICS
Instruments rarely respond instantaneously to changes in the measured variables. Instead, they exhibit
slowness or sluggishness due to such things as mass, thermal capacitance, fluid capacitance or electric
capacitance. In addition to this, pure delay in time is often encountered where the instrument waits for
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some reaction to take place. Such industrial instruments are nearly always used for measuring quantities
that fluctuate with time. Therefore, the dynamic and transient behavior of the instrument is as important
as the static behavior.
The dynamic behavior of an instrument is determined by subjecting its primary element (sensing
element) to some unknown and predetermined variations in the measured quantity. The three most
common variations in the measured quantity are as follows:
l. Step change in which the primary element is subjected to an instantaneous and finite change in
measured variable.
2. Linear change, in which the primary element is following a measured variable, changing linearly with
time.
3, Sinusoidal change, in which the primary element follows a measured variable, the magnitude of
which changes in accordance with a sinusoidal function of constant amplitude
.
The dynamic characteristics of an instrument are (i) speed of response,
(ii) Fidelity, (iii) lag, and (iv) dynamic error.
(i) Speed of Response: It is the rapidity with which an instrument responds to changes in the measured
quantity.
(ii) Fidelity: It is the degree to which an instrument indicates the changes in the measured variable
without dynamic error (faithful reproduction).
(iii) Lag: It is the retardation or delay in the response of an instrument to changes in the measured
variable.
(iv) Dynamic Error: It is the difference between the true values of a quantity changing with time and
the value indicated by the instrument, if no static error is assumed.
When measurement problems are concerned with rapidly varying quantities, the dynamic relations
between the instruments input and output are generally Defined by the use of differential equations
2. What are the different types of static errors in a system?
Ans:
The static error of a measuring instrument is the numerical difference between the true value of a
quantity and its value as obtained by measurement, i.e. repeated measurement of the same quantity give
different indications. Static errors are categorized as gross errors or human errors, systematic errors and
Random errors.
1. Gross Errors
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GRIET/ECE 3
This error is mainly due to human mistakes in reading or in using instruments or errors in recording
observations. Errors may also occur due to incorrect adjustments of instruments and computational
mistakes. These errors cannot be treated mathematically. The complete elimination of gross errors is not
possible, but one can minimize them .Some errors are easily detected while others may be elusive. One
of the basic gross errors that occur frequently is the improper use of an Instrument the error can be
minimized by taking proper care in reading and recording the measurement parameter. In general,
indicating instruments change ambient conditions to some extent when connected into a complete
circuit.
2. Systematic Errors
These errors occur due to shortcomings of, the instrument, such as defective or worn parts, or ageing or
effects of the environment on the instrument.
These errors are sometimes referred to as bias, and they influence all
measurements of a quantity alike. A constant uniform deviation of the operation of an instrument is
known as a systematic error. There are basically three types of systematic errors
(i) Instrumental, (ii) Environmental, and (iii) Observational
(i) Instrumental Errors
Instrumental errors are inherent in measuring instruments, because of their mechanical structure. For
example, in the D'Arsonval movement friction in the bearings of various moving components, irregular
spring tensions, stretching of the spring or reduction in tension due to improper handling or over loading
of the instrument. Instrumental errors can be avoided by
(a) Selecting a suitable instrument for the particular measurement applications.
(b) Applying correction factors after determining the amount of instrumental error.
(c) Calibrating the instrument against a standard.
(ii) Environmental Errors
Environmental errors are due to conditions external to the measuring device, including conditions in the
area surrounding the instrument, such as the effects of change in temperature, humidity, barometric
pressure or of magnetic or electrostatic fields.
These errors can also be avoided by (i) air conditioning, (ii) hermetically sealing certain components in
the instruments, and (iii) using magnetic shields.
(iii) Observational Errors
Observational errors are errors introduced by the observer. The most common error is the parallax error
introduced in reading a meter scale, and the error of estimation when obtaining a reading from a meter
scale.
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These errors are caused by the habits of individual observers. For example, an observer
may always introduce an error by consistently holding his head too far to the left while reading a needle
and scale reading.
In general, systematic errors can also be subdivided into static and dynamic Errors. Static
errors are caused by limitations of the measuring device or the physical laws governing its behavior.
Dynamic errors are caused by the instrument not responding fast enough to follow the changes in a
measured variable.
3. What is the method used to calculate the errors in an instrument?
Ans:
ERROR IN MEASUREMENT
Measurement is the process of comparing an unknown quantity with an accepted
standard quantity. It involves connecting a measuring instrument into the system under consideration
and observing the resulting response on the instrument. The measurement thus obtained is a quantitative
measure of the so-called "true value" (since it is very difficult to define the true value, the term
"expected value" is used). Any measurement is affected by many variables; therefore the results rarely
reflect the expected value. For example, connecting a measuring instrument into the circuit under
consideration always disturbs (changes) the circuit, causing the measurement to differ from the expected
value. Some factors that affect the measurements are related to the measuring instruments themselves.
Other factors are related to the person using the instrument. The degree to which a measurement nears
the expected value is expressed in terms of the error of measurement. Error may be expressed either as
absolute or as percentage of error. Absolute error may be defined as the difference between the expected
value of the variable and the measured value of the variable, or
e = Y n - X n
Where e=absolute errors;
Yn=expected value;
Xn=measured value;
Therefore %error = (absolute value/expected value )*100=(e/Yn)*100
Therefore %error=
It is more frequently expressed as an accuracy rather than error.
Therefore A=1-
Where A is the relative accuracy
Accuracy is expressed as % accuracy
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GRIET/ECE 5
a=100%-%error
a=A*100% (where a=%accuracy)
4. Describe the function of the DC-Voltmeter and multi range voltmeter and explain
their operation?
Ans: DC-Voltmeter
A basic D'Arsonval movement can be converted into a dc voltmeter by adding a series
resistor known as multiplier, as shown in the figure. The function of the multiplier is to limit the
current through the movement so that the current does not exceed the full scale deflection value.
A dc voltmeter measures the potential difference between two points in a dc circuit or a circuit
component. To measure the potential difference between two points in a dc circuit or a circuit
component, a dc voltmeter is always connected
across them with the proper polarity. The value of
the multiplier required is calculated as follows.
Im: full scale deflection current of the movement
Rm : internal resistance of movement
Rs : Multiplier resistance
V: full range voltage of the instrument
From the circuit of Fig. 4.1
V= Im *( Rm+ Rs)
Rs = = -
therefore Rs = -
The multiplier limits the current through the movement, so as to not exceed the value of the full scale
deflection Ifsd.
The above equation is also used to further extend the
range in DC voltmeter'.
Multi range Voltmeter:
As in the case of an ammeter, to obtain a
multi range ammeter, a number of shunts are connected
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GRIET/ECE 6
across the movement with a multi-position switch.
Similarly, a dc voltmeter can be converted into a
multi range voltmeter by connecting a number of
resistors (multipliers) along with a range switch
to provide a greater number of workable
ranges. The below Figure shows a multi range
voltmeter using a three position switch and three
multipliers R1, R2, and R3, for voltage values
V1, V2, and V3. Fig 4.2 can be further modified to
multipliers connected in series string, which is a
more practical arrangement of the
multiplier resistors of a multi range voltmeter. In
this arrangement, the multipliers are connected in a series string, and the range selector selects the
appropriate amount of resistance required in series with the movement.
This arrangement is advantageous compared to the previous one, because all multi1llier resistances
except the first have the standard
resistance value and are also easily
available in precision tolerances. The
first resistor or low range multiplier,
R4, is the only special resistor which
has to be specially manufactured to
meet the circuit requirements.
5. Explain the working of solid
state voltmeter?
Ans:
The below figure shows the circuit of
an electronic voltmeter using an IC Op
Amp 741C.This is a directly coupled
very high gain amplifier. The gain of
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GRIET/ECE 7
the Op Amp can be adjusted to any suitable lower value by providing appropriate resistance between its
output terminal, Pin No. 6, and inverting input, Pin No. 2, to provide a negative feedback. The ratio R2
/R1 determines the gain, i.e. 101 in this case, provided by the Op Amp. The 0.1 pF capacitor across the
100 k resistance R is for stability under stray pick-ups Terminals 1 and 5 are called offset null terminals.
A 10 kΩ potentiometer is connected between these two offset null terminals with its centre tap
connected to a - 5V supply. This potentiometer is called zero set and is used for adjusting zero output for
zero input conditions.
The two diodes used are for IC protection. Under normal conditions, they are non-conducting, as the
maximum voltage across them is l0 mV. If an excessive voltage, say more than 100 mV appears across
them, then depending upon the polarity of the voltage, one of the diodes conducts and protects the IC. A
μA scale of 50 - 1000 μA full scale deflection can be used as an indicator. Ro is adjusted to get
maximum full scale deflection.
6. Draw the block diagram of the measuring system and explain the
function of each stage of this system?
Ans:
The generalized measuring system consists of three main functional elements. They are,
1. Primary sensing element, which senses the quantity under measurement.
2. Variable conversion element, which modifies suitably the output of the primary sensing element
3. Data presentation element that renders the indication on a calibrated scale.
1. Primary Sensing Element
The measurement first comes into contact with primary sensing element where the conversion takes
place. This is done by a transducer which converts the measurement (or) measured quantity into a usable
electrical output. The transduction may be from mechanical, electrical (or) optical to any related form.
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2. Variable Conversion Element
The output of the primary sensing element is in the electrical form suitable for control, recording and
display. For, the instrument to perform the desired function, it may be necessary to convert this output to
some other suitable for preserving the original information. This function is performed by the variable
conversion element. A system may require one (or) more variable conversion suitable to it.
(a) Variable Manipulation Element
The signal gets manipulated here preserving the original nature of it. For example, an amplifier accepts a
small voltage signal as input and produces a voltage, of greater magnitude. The output is the same
voltage but of higher value, acting as a voltage amplifier. Here the voltage amplifier acts as a variable
manipulation element since it amplifies the voltage. The element that follows the primary sensing
element in a measurement system is called signal conditioning element. Here the variable conversion
element and variable manipulation element are collectively called as Data conditioning element (or)
signal conditioning element.
(b) Data Transmission Element
The transmission of data from one another is done by the data transmission element. In case of
spacecrafts, the control signals are sent from the control stations by using radio signals.
The stage that follows the signal conditioning element and data transmission element collectively is
called the intermediate stage.
(c).Data Presentation Element
The display (or) readout devices which display the required information about the measurement, forms
the data presentation element. Here the information of the measurand has to be conveyed for,
monitoring, Control (or) analysis purposes.
(a). 1t case of data to be monitored, visual display devices are needed like ammeters; voltmeters and so
on are used.
(b)In case of data to be recorded, recorders like magnetic tapes, T.V equipment, and storage type C.R T,
printers and so on are used.
7. Explain the types of test signals used in determining dynamic characteristics of
measurements applied to a system.
Ans:
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Electronic Measurements & Instrumentation Question & Answers
GRIET/ECE 9
The a dynamic characteristic (or) analysis is classified with respect to time and frequency as time
domain analysis and frequency domain analysis
(a).In time domain analysis the i/p is applied to the system and the behavior of the system is studied as a
function of time.
(b) In frequency, domain analysis the i/p is a sinusoidal one and the behavior of the system is studied as
a function of frequency.
The standard test signals used for time domain analysis are as follows.
(i) Step input
(ii) Ramp input
(iii) Parabolic input
(iv) Impulse input.
(i) Step Input
The continuous time step input u (t) is defined as the discrete time step input a[n] is defined as,
U (t) = and discrete time step input u[n] is defined as, u (n) =
Therefore, a unit step input represents a signal which changes its level from 0 to I in zero time and. it
reveals a great deal about how quick, the system responds to an abrupt change in the input signal
(ii) Ramp Input
The ramp input is defined in continuous time as
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GRIET/ECE 10
r (t) =
and r[n] =
(iii) Parabolic Input
The parabolic input is defined as,
r (t) =
and the discrete time is defined as,
r[n] =
The signal are given below,
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GRIET/ECE 11
This signal is also called as acceleration input since the input signal is proportional to represents a
constant acceleration.
(iv) Impulse Input
It is also called as a δ (delta) function. The continuous time impulse input is given by, square of
time and
δ (t) =0 for t≠0
And discrete time impulse input is given by,
δ (n) =
The unit impulse is defined as the signal which has a zero value everywhere except at t=0.where the
magnitude is finite.
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GRIET/ECE 12
In frequency domain analysis, the system behavior is studied through the sinusoidal signal because the
time varying signals such as step, ramp, and parabolic inputs can be expressed in terms of sinusoidal
signal of differential amplitudes and frequencies.
A continuous time sinusoidal signal is given as
X(t)=A sin(ωt + φ)
Where A= amplitude
ω = frequency in radians/sec.
φ = phase angle in radians.
A sinusoidal signal is an example of a periodic signal, the period of which is T=
The discrete time version of a sinusoidal signal is given by,
X[n] =A sin (ωn + φ)
Where, ω = angular frequency in radians/cycle.
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GRIET/ECE 13
8. Explain the terms
(i). significant figures
(ii). Conformity
Ans:
(i) Significant Figures
The number of meaningful digits used to express a numerical value (measured value of a quantity) are
known as, significant figures. Significant figures indicate the precision of the measurement and the
magnitude of the measurements. The measured value should be expressed in more number of significant
figures because the more significant figures the higher will be the precision.
Consider an example in which the measured voltage across a resistor in a circuit is specified as
50 V. It indicates that the measured voltage may be close to 49 V or 51 V. This specification has two
significant figures. If the measured voltage is specified as 50.0 V then it indicates that the value may be
close to 49.9 V or 50. 1 V. This specification has three significant figures. From the above illustration, it
can be observed that the specification with three significant figures is more precise than the one with
two significant figures.
(ii) Conformity
Conformity is one of the characteristics which determine the precision. If a measuring instrument
consistently and repeatedly provides a value as close to the true value (of the measured quantity) as an
observer can estimate the true value from its scale reading then this characteristic refers to the
conformity of the measurement. Let us consider an example of measuring resistance of a resistor which
has a true resistance of 10,654,739 Ω). If the multi meter indicates the resistance value as 10.7 MO
consistently and repeatedly, then the condition of conformity is satisfied. But, due to the limitation of
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GRIET/ECE 14
scale reading, there exists an error in the measured value as the scale provides the reading up to one
decimal place only.
Thus, conformity is a necessary condition, but not a sufficient condition for the
measurement to be precise.
9. What is ayrton shunt? Describe it with a neat sketch .specify its application?
Ans:
Aryton shunt: It is also known as universal shunt. Figure shows the basic circuit of an aryton
shunt.
It avoids the possibility of using the meter in the circuit without a shunt. This is the most
important merit of the aryton shunt.
From the above figure, it is noted that the series combination of resistors R2, R3 and the meter
movement is in parallel with R1 when the switch (SW) is connected to position "1". Therefore, the
current through the meter movement is less than the current through the shunt, thereby protecting the
meter movement. This reduces the sensitivity of meter movement. The series combination of resistor R6
and the meter movement is in parallel with resistor R1, R2, when the SW is connected to position "2".
Therefore, the current through the shunt resistance is less than the current through the meter movement.
The resistors R1, R2, and R3, are together in parallel with meter movement. When the switch is in
position "3".Now the current flowing through the shunt is very little whereas the current flowing through
the meter is very high. Hence the sensitivity of the meter movement is increases.
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10. Explain with a neat block diagram of a dual slope digital voltmeter?
Ans:
Basic Principle:
Initially, the dual slope integrating type DVM integrates the input voltage Vi. The slope of the integrated
signal is proportional to the input voltage under measurements .after certain period of time say t1 the
supply of input voltage Vi is stopped, and a negative voltage -Vr of the integrator. Then the output
signal of integrator will have negative slope, and is constant and also proportional to the magnitude of
the input voltage.
BLOCK DIAGRAM AND WORKING:
The major blocks of a dual slope integrating type
DVM (dual slope analog to digital converter) are,
1. An op-amp employed as an integrator
2. A level comparator
3. Oscillator for generating time pulses
4. Decimal counter
5. Block of logic circuitry.
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Initially a pulse is applied to reset the counter and the output of flip-flop will be at logic '0'. The switch
Sr is in open condition and the switch, Si is in closed condition. Now, the capacitor 'C' starts to charge.
Once the output of the integrator becomes greater than zero, the output state of the comparator changes
which in turn opens the AND gate .When the gate opens the output of the oscillator (clock pulses) are
allowed to pass through it and applied to the counter. Now the counter counts the number of pulses fed
to it. As soon as it reaches its maximum count that is the counter is preset to run for a time period r,, in
this condition the maximum count will be'9999', and for the next immediate clock pulse the count
changes or goes to '0000' and the flip-flop will be activated. Therefore, the output of flip flop becomes
logic 'I' which in turn activates the switch drive circuitry. This makes the switch Si, to open and Sr to
close (i.e., the supply of Vi will be stopped. and the supply of V is applied to the integrator) with this
applied signal the output of the integrator will be a constant negative slope i.e., its output signal linearly
decreases to zero. This again makes the output of the comparator to change its state which in turn closes
the gate. Here, the discharging time t2 of the capacitor is proportional to the input voltage signal Vi
.During this discharging period the counter indicates the count. As soon as, the negative slope reaches
zero volts the comparator changes its output state to 'zero' which in turn locks the gate. Once, the output
of integrator becomes zero (or the input of the comparator is zero) the counter will be stopped. And the
counted pulses are displayed (which directly gives the input voltage).
From the above equation, it is clear that the measured voltage signal's accuracy does not depend on the
time constant of the integrator.
Advantages
1. Depending on the requirement the accuracy and sped can be varied.
2. It can provide the output with an accuracy of +-0.005% in 100ms
3. This technique exhibits excel lent noise rejection since the integration process eliminates both noise
and super imposed A.C.
11. Explain the constructional details and differentiate between Ohmmeter series
type and shunt type. ?
Ans: ohmmeter (SERIES TYPE OHM METER)
A D'Arsonval movement is connected in series with a resistance R, and a battery which is connected to a
pair of terminals A and B, across which the unknown resistance is connected. This forms the basic type
of series ohm meter, as shown in the fig 11.
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The current flowing through the movement then depends on the magnitude of the unknown resistance.
Therefore, the meter deflection is directly proportional to the value of the unknown resistance
referring to the figure 11.
R1: current limiting resistance
R2: zero adjust resistance
V= battery
Rm =meter resistance
Rx=un know resistance
Calibration of the Series Type Ohmmeter:
To mark the "0" reading on the scale, the terminals A and B are Shorted, i.e. the
Unknown resistance Rx=0, maximum current flows in the circuit and the shunt Resistance R2 is adjusted
until the movement indicates full scale current (Ifsd ). The Position of the pointer on the scale is then
marked "0" ohms. Similarly, to mark the "∞" reading on the Scale, terminals A and B are open, i.e., the
unknown resistance Rx=∞, no current flow in the circuit and there is no deflection of the pointer. The
position of the pointer on the scale is then marked as “∞” 0hms.
By connecting different known values of the unknown resistance to terminals A
and B, intermediate markings can be done on the scale. The accuracy of the Instrument can be checked
by measuring different values of standard resistance, i.e., the tolerance of the calibrated resistance, and
noting the readings a major drawback in the series ohmmeter is the decrease in voltage of the internal
battery with time and age. Due to this, the full scale deflection current Drops and the meter does not read
"0" when A and B are shorted. The variable Shunt resistor R2 across the movement is adjusted to
counteract the drop in battery Voltage. There by bringing the pointer back to "0" ohms on the scale'
It is also possible to adjust the full scale deflection current without the shunt R2 in
the circuit, by varying the value of R1, to compensate for the voltage drop. Since this value affects the
calibration of the scale, varying by R2 is much better solution. The internal resistance of the coil Rm is
very low compared to R1 When R2 is varied, the current through the movement is increased and the
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current through R2 is reduced, thereby bringing the pointer to the full scale deflection position. The
series ohmmeter is a simple and popular design, and is used extensively For general services work,
Therefore ,in a series ohmmeter the scale marking on the dial has “0” on the right side ,corresponding to
full scale deflection current ,and "∞" on the left side corresponding to no current flow as given in the fig
11.1 Values of R1 and R2 can be determined from the value of Rx ,which gives half the full scale
deflection.
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PDMS Syntax



In principle, any attribute can be set by specifying the attribute name and value you want it to take. The following are examples:

XLEN  200
HEIGHT  300
NAME  /FRED
ORI  Y  IS  N
DESC  'PLATE  GIRDER'
TEMP  120
PURP  EQUI
ORI  Y  IS  N  AND  Z  IS  U

 
Navigation
Commands for moving around the PDMS database.
/NAME
Move to an element by name
=23/506
Move to an element by its reference number
END
Move up the database hierarchy by 1 level
6
Move to the sixth element in the list of the current element
NEXT
Move to the next element in the list at the same level
NEXT 2
Move to the second element after the current element
NEXT ELBO
Move to the next elbo in the current list by passing any other elements
PREV
Move to the previous element in the list
PREV 4
Move four elements back from ce
SAME
Go to the previous current element
 
NOTE: NEXT and PREV commands work on the list according to the modes Forwards or Backwards. In backwards mode, the list is considered to be reversed so these commands have the effect of working from the opposite end of the list.
 
Query Commands
Q ATT
Query all the attributes of the current element
Q POS
Query the position of the current element
Q POS IN SITE (or Q POS WRT SITE)
Query the position of the current element relative to the site position
NOTE: Normally, the Q POS command gives the position relative to the element's owner.
Q NAME
Query the name of the current element. This may either begin with '/' character '/PIPING' or may be by a list position name (full name) such as:
ELBO 2 OF /P1/B1
Q REF
Query the database unique reference number i.e. = 234/702. This is the best way of ensuring that you get to the element you want. Names can change but reference numbers are fixed so you always get the same element.


 Positioning Commands (General)
At E300 N400 U500
Position an element explicitly at the coordinates given relative to the element's owner. To position relative to some other element, wrt can be added, as shown
At E3333 N6000 U50 WRT SITE
At N500W30U600 WRT WORLD
AT N400 U500 E300 IN ZONE                                                           
At N40 WRT /FRED
BY N500
Move the element north from it's current position by 500mm (This is relative movement.)
CONN P1 TO P2 OF PREV
Positions P1 at the specified point and orientates the element such that P1 is pointing in the opposite direction to the specified ppoint.
CONN IDP@ TO IDP@
Connect a picked Ppoint on the current primitive to a picked Ppoint of another
CONN P1 TO IDP@
Connect P1 of the current primitive to a picked Point of another primitive
 Move syntax
Position>Move>Distance
Moves the element’s origin by a given distance in a given direction.

Ex.       MOVE N DIST 10’                  MOVE S WRT /* DIST 5'                   MOVE E IN SITE DIST 5'

Position>Move>Through
Moves the origin of the element in a given direction through a Reference Plane perpendicular to the line of travel that is passing through a picked element, p-point, or coordinate.

Ex.       MOVE N THRO ID@ MOVE N THRO IDP@          MOVE N THRO N46’

Position>Move>Clearance
Moves the element’s origin, p-point, or obstruction in a given direction with a clearance from another item’s origin, p-point, or obstruction
.
Ex.  MOVE E DIST 10’ FROM /P-101                    MOVE E CLEARANCE 10’ FROM /P-101

The options INFRONT, BEHIND, ONTO, and UNDER refer to a picked or named item’s physical obstruction, while the TO and FROM options refer to the item’s origin.  INFRONT and TO refer to the near side while BEHIND and FROM refer to the far side of an item.

Position>Plane Move>Through
Moves the origin of the element in a given direction through a Reference Plane specified by the user that is passing through a picked element, p-point, or coordinate.

Ex.       MOVE ALONG E PLANE N45W THRO ID@

Positioning Commands (Piping)
NOTE: All the above commands can be used with piping components for exact positioning. The following commands are specific to piping because they use the implied direction of the previous component to determine the position. This implied direction is some times referred to as the constrained centreline and is simply a line drawn in the direction of the previous component. All of the following commands will move components along this line.
DIST 300
Position the current element 300mm away from the previous component. The direction is taken as the leave direction of the previous component.
CLEAR 400
Position the current element with a clearance of 400m between it and the previous element. For most types of component, this command gives a tube spool length equal to the clearance value. For some components such as level operated valves the clearance is likely to take the lever length as the obstruction length of the valve, so in this case the clearance might be more unpredictable.
THRO N500
TO N500
Position the origin of the CE along constrained centerline through N500 in ZONE coordinates.
THRO PT
Position the origin of the CE along constrained centerline at the point where it intersects a perpendicular plane positioned at  the branch tail.
CONNect
Position the arrive point at the leave point of the previous component and orientate the component to suit.

 
Orientation Commands (General)
ORI Y IS N AND Z IS U
This is the default orientation (wrt owner) for all elements that have an orientation attribute.
ORI Y IS E45N
Specify that the Y axis is pointing E45N. When only one axis is specified, the other tries to get to it's default, so in this case, Z will default to UP.
ORI P1 IS N
Rather than specifying an axis, this command specifies that a particular ppoint is to be orientated in the direction specified.

 
Orientation Commands (Piping)
ORI
This command orientates the arrive of the element in the opposite direction to the leave of the previous element. It does not change the position.
CONNECT
Perform an ORI, then position the arrive at the leave of previous.
DIR S
This is a special command which is allowed to change the angle of a component. It first performs an ori, then adjusts the angle to ensure that the leave direction is in the direction specified.
ORI AND P3 IS U
Used for valves, tees, etc., this command performs an ori and then points the ppoint in the required direction. It does not change the angle.
DIR AND P3 IS U
This is another special command which is only used on tees with variable angles. (Usually for sloping lines.) In this case, the tee is orientated and the angle adjusted to allow p3 to point in the direction specified.

 
Creating Elements
NEW  BOX
To create anything in PDMS, you need to be at the right level in the hierarchy and use the command NEW followed by the TYPE of element you want to create.
NEW  EQUI  /T-1101
Create EQUI element and set the name attribute
NEW ELBO CHOOSE
For piping components, you need to create the element and then link it to the catalogue via the spref attribute. The CHOOSE command allows you to select components from the specification by picking them from a displayed menu.
CHOOSE ALL
Allows you to see more detail about the component than CHOOSE on it's own.
 
Deleting Elements
DELETE ELBO
To delete an element, the syntax is DELETE followed by the TYPE of element you are deleting.
DELETE BRAN MEM
This deletes the members of an element (i.e. BRAN in this example) without deleting the element itself.
 
PSEUDO ATTRIBUTES
  In order to get specific information directly from the database, a number of keyword or pseudo attributes have been introduced. Pseudo attributes are not attributes as such, but they have the ability to extract data when queried. For Example
ELBO 1
Go to elbo 1 of the branch
Q PARAM
Query the parameters of the catref of the spref
Q DTXR
Query the rtext of the detref of the spref_ can also use dtxs or dtxt
Q MTXX
Query the xtext of the matref of the spref _ can also use mtxy or mtxz
Q PSATTS
Query the list of pseudo attributes available for the CE.
 
A few useful pseudo attributes appear below:
  General Queries
Q LIST
Query what you can create below the current element
Q OLIST
Query the type of elements which can own CE
Q ORDER
Query the list position
Q PROP DESC
Query the data element with the dkey equal to DESC in the component's dataset (Steelwork and Piping elements)
Q PRLS
Query the list of properties in the component's dataset
Q PURP XXX
Query the purpose attribute of the property XXX
  Piping Attributes
Q CHOICE
Query the answers of the selectors of the spref
Q CHOICE STYP
Query the styp used to select the component
Q PL BOP
Query the bottom of pipe elevation of the leave point
Q PA INSU
Query the insulation thickness at the arrive point
Q PGRAD 1
Query the slope at ppoint 1
Q ITLE
Query the length of implied tube (must navigate first by using 'IL TUBE' at a component)
Q LBOR
Query the leave bore
Q ABOR
Query the arrive bore
Q APOS
Query the arrive position
Q LPOS
Query the leave position
At Branch Level
Q TULEN
Query the length of tube in a branch
Q CLLEN
Query the centerline length through all components
  Steelwork 
Q ODESP
Query the design params of the joint owner
Q ADESP
Query the design params of the joint attached beam
Q DRPS
Query the derived position of the beam start
Q NWEI
Query the net weight (considering joint cut outs)
Q GWEI
Query the gross weight (beam before cutting)
Q NCOF
Query the net centre of gravity for the beam
Q NSRF
Query the net surface area
Q MIDP
Query the mid point
Q POS PPLINE TOS START WRT /*
Query TOS of current element (SCTN)
Q PPLINE TOS DIR
Query the direction of the TOS pline on a SCTN
 
The Construct Syntax
The construct syntax is described more fully in the Design reference manual and it is worth looking at it in more detail. CONST allows distances and angles to be calculated from the design data and is invaluable when you are writing applications. For example
Q CONST ANGLE N AND W
gives 90°
CONST A PIN1 TO PIN2 TO PIN3

Q CONST DIST FROM P1 to P2 TO P2 OF/BOX1
gives a distance
CONST DIST FROM PA TO PL OF PREV

  $S  QA=Q  ATT                   Create a synonym to query attributes
Q  EVAR  PDMSUSER        Query the operating system location of user file directory PDMSUSER
Reporting Syntax
You can create an array which includes a number of elements which all satisfy specific selection criteria, as defined by yourself. The syntax is:
VAR !Array COLLECT selection criteria
!Array is the name of the array that will be created to contain the elements selected.
The following general criteria can be used to define the selection:
  • A class of elements or element types
  • A logical expression to be satisfied at all selected elements
  • A physical volume in whichall selected elements must lie
  • A point in the hierarchy below which all selected elements must lie
Eg VAR !PIPECOMPS COLLECT ALL BRANCH MEMBERS
This would create the array !PIPECOMPS and set it to contain the reference numbers of every piping component in the MDB. Logical expressions use the WITH and WHERE option; a volume is defined by the WITHIN keyword; and the hierarchy criteria is defined by the FOR keyword.
Eg VAR !ELBO COLL ALL ELBO WITH SPREF EQ /A300B/100
Evaluating Selected DB Elements
Using the facilities described here you can create an expression and have it evaluated for all elements which satisfy particular selection criteria. The results of the expression are then placed in a named array.
The command syntax is:
VAR !Array EVALUATE (Expression) FOR Select
!Array is the name of the array that will be created
(expression) is the expression that will be carried out for all elements that match the select criteria
Select is the selection criteria
Eg VAR !BOXES EVALUATE ( XLEN * YLEN ) FOR ALL BOXES
 
IF ALL ELSE FAILS!
 
As you can see, there are a lot of commands available to the PDMS user and the list above is only scratching the surface. Almost all of the command syntax is described in the reference manuals but in some cases you might find it difficult to compose the required command from these alone. In these cases, it might be necessary to build a command by using the query syntax itself, using $Q and $H syntax.
The command: $Q gives a list of all possible commands at any one time. On it's own, $Q gives a complete list of top level commands in any PDMS module. When applied in the middle of a command line, it lists the options available at that point.
E.G. the command:
SETUP FORM
Yields an error incomplete command line
SETUP FORM $Q
list_name as required
SETUP FORM _FRED $Q
lists a number of options including:
'BLOCK/ING' 'RESI/ZABLE' 'AT' 'SIZE' 'COPY' and Newline
 
Each of the words in quotes can be used at this point. There may be further options after these words and the same technique can be used to find the way through. The characters before the '/' indicate the minimum abbreviation which may be used for each part of the command. The presence of the Newline keyword without the quotes indicates that the return key may be pressed at this point and the command is executed.
Another form of syntax querying is the $H command. $H is a slightly more sophisticated form of $Q, which lists the available options numerically as the following example shows:
SETUP $H
1 <create a new form>
SETUP $H1
'FORM'
SETUP FORM $H
UNAME
And so on.