Trouble gathering accurate strain data

[Badger12]

Hi everyone! 

I am utilizing a quarter bridge strain gage from Omega (G.F: 2.1, and 120 ohm) connected to a NI9944, which is then connected to a NI9237, housed in a cDAQ-9171 which connects to my computer. My issue is that when I open labview and attempt to set it up in labview the strain value I get is roughly -725m (images attached). I have no prior experience with labview and have been following YouTube videos and reading documentation (http://www.ni.com/tutorial/52796/en/) for example. I have tried using different slots on the DAQ, fixing the gage to a piece of aluminum, and even letting the gage dangle freely but constantly have high values which prevent me from being able to calibrate. Any and all help would be greatly appreciated, thank you! 

[Badger12]

Hi everyone,

I am trying to gather strain data and am using a NI 9944 connected to a NI 9237. During my initial setup to gather data I was using a NI 9171 to connect to my computer. With this setup I was able to gather strain data that was on the same order of magnitude and was somewhat close to what SolidWorks was telling me the strain should be. The issue is that I need to gather more data points at the same time, which requires the use of additional NI 9237, I was able to obtain a NI 9174 to house all of these DAQs, my issue is that when I take the 9237 and put it into the new chassis, with the same experimental setup and code I am off by a a factor of 10. I did go back into my LabView code and ensure that the DAQ assistant is taking data from the correct channel. 

I am wondering, what am I missing? Any and all suggestions/help is greatly appreciated! 

[Badger12 · Accepted solution]

I ended up using a DAQ assistant to take an initial measurement then subtracted that value from all subsequent data. It got me into the ballpark with respect to what SolidWorks was telling me the strain should be.