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Zero strain readings at the start of a test using Daq Assistant

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To plot force vs. strain, acquire an array of each, then bundle the two one-dimensional arrays together and wire that cluster to an XY Graph.  That should give you the plot you're looking for.

 

Here are some links from the online help:

http://zone.ni.com/reference/en-XX/help/371361K-01/lvconcepts/types_of_graphs_and_charts/#XY_Graphs

http://zone.ni.com/reference/en-XX/help/371361K-01/lvhowto/graphing_xy_data/

-Jim B
Applications Engineer, National Instruments
CLD, CTD
Message 11 of 34
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Hi James,

 

 

               Thank you for the Info, Can you provide me with a sample VI??. I am kinda new to labview.

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Message 12 of 34
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Here's a good community example,

 

https://decibel.ni.com/content/docs/DOC-18312

 

but instead of the sine and sinc functions, you would feed your acquired data in.

-Jim B
Applications Engineer, National Instruments
CLD, CTD
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Message 13 of 34
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Thanks Jim,

 

             Can i give inputs from DAQ Assistants ( one for force and the other for strain ) instead of sine and sinc functions.

 

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Message 14 of 34
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James already said you could. If you stick with the DAQ Assistant, just use the split signal function. You can stick with express functions with the express xy graph.

Have you taken any of the free tutorials? Your questions are very basic.
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Message 15 of 34
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Hi Carlos,

 

              I have a question. I used a half bridge strain gauge circuit to get the strain values. Is the graph generated in labview giving you the total strain reading of both the strain gauges or the strain reading of a single strain gauge. If it is giving the total strain values, then how to get the strain values of the individual strain gauges.

 

Thank you

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Message 16 of 34
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Are your strain gauges set up in Half-Bridge configuration I, II, or III?  These different options are documented very well here: http://www.ni.com/white-paper/4172/en/

 

Also documented in that white paper is how strain(e) is calculated from the measured voltages.

-Jim B
Applications Engineer, National Instruments
CLD, CTD
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Message 17 of 34
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it is half bridge type II.. but the graph is showing only one signal. is it giving me the strain reading of both the strain gauges?. the value is 2x10^-6. is it the strain of one strain gauge or addition of both ( 3x10^-6 + 3*10^-6 )




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Message 18 of 34
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You really need to provide some details. What are the physical connections that you made? Attach an image of your block diagram as well. Of you are using the DAQ Assistant, attach an image that shows how you have configured it. If you only see a single channel on a graph, it's because your acquisition only reads a single channel or you removed acquired data before you plotted it. You should be able to debug both of these situations on your own.
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The returned value will be the strain (e).  It is using information from both gauges to calculate the strain on the object they are connected to.  It is calculated by the equation in the white paper attached above.

-Jim B
Applications Engineer, National Instruments
CLD, CTD
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