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

[fwowe]

I have been working on a code which utilizes daqmx assistant to read and write strain, temperature and voltage from a cdaq-9174, with cards NI 9211 and NI 9237.  Everything works fine in the code but I want to be able to zero the strain data at the start of a test.

I have been trying to create a way to make it so I click a button and it will zero just the strain data like an autobalance.  Does anyone have any suggestions on how to accomplish this?

[Carlos_O · Accepted solution]

Hi Fwowe,

From what I understand, you are trying to to have is a tare. I've programmed a little VI that acomplishes that task.

Take a look at it and tell me what you think.

Best Regards!

Carlos O

Applications Engineer

National Instruments

[fwowe]

Thanks Carlos that was exactly what I needed.

[djemb]

Can you post a picture of your vi? Using LabVIEW 8.5.1, I currently capture the output of the DAQ Assistant in a Waveform Graph and then substract it from the data. This works but sometimes the vi crashes and I'm curious about your solution.

[Carlos_O]

Hi djemb!

I hope this helps!

Kind Regards

Carlos O

Applications Engineer

National Instruments

[djemb]

Thank you Carlos, do you have a suggestion to do the same thing with DDT? Our DAQ Assitant is configured to collect 6 strains gages at 20 Hz with 5 sample deep buffer.

[Carlos_O]

Hi djemb!

You might want to try to use this code as a subVI in your original program. Take a look here to see how to create subVIs in LabVIEW 2011.

I hope this helps.

Cheers!

[ManjunathaPrasad]

Hi Carlos,

          Thank you for the VI that you posted online to zero strain. By using the VI that you provided, i tried to zero out the strain. But i am not able to get any kind of strain readings in the output ( Waveform Chart ). Attached is the block diagram. Can you please suggest me the changes that needs to be made in this

[Dennis_Knutson]

Your VI is not at all the same as the posted example. Get rid of that inner loop around the DAQ Assistant.

[ManjunathaPrasad]

Thank you,

              Got rid of it and it is working perfectly fine. I have a question though. How to plot force v/s strain graph in Labview? I have a NI 9237 to measure the strain and a load cell to measure the deflection. Can i know how to synchronize both the signals and get a graph of Force v/s Strain?. I need help with the VI. Would greatly appreciate if you post the VI for me