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IEPE Triaxial Accelerometer Issues with NI 9234 Module

Hello NI Community,

 

I am attempting to connect an Omega ACC 301A triaxial accelerometer with an NI 9234 DAQ module. This accelerometer uses a four pin connector, so I am using a 4 pin connector to 3 BNC terminal cable to connect to the 9234 module. On the spec sheet for the Omega ACC 301A, it states an excitation current of 2 - 6mA @ 15 to 30 VDC, which is in the range of my NI 9234 card and an amplitude range of +/-5 V, which is also in the range of the NI 9234. 

 

In the DAQ assistant, I have all constants set per the accelerometer spec sheet, but when I run the VI, the X axis does not respond to any motion, and the Y and Z axes seem to drift when the accelerometer is motionless. I have attached my VI to this post as well as a screenshot showing a real time plot of data. In the screenshot, the triaxial accelerometer is motionless yet has an almost sinusoidal curve present between -.1 Gs to 0 Gs. 

 

Does anyone know what might be causing this drift on the accelerometers voltage output? Also any reason why the X axis wouldn't respond? This is a brand new accelerometer that was calibrated within the last month.

 

I have used this same NI 9234 card with other IEPE triaxial accelerometers with no issues. Any advice would be greatly appreciated!

 

Thanks,

Chris

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Hi cj,

 

Everything looks correctly configured in your DAQ Assistant in LabVIEW. You could try using a scope on the BNC of the X-axis measurements to verify that the accelerometer is actually outputting information. You said it was recently calibrated but it wouldn't hurt to double check. Do the Y and Z axes show drift while the accelerometer is in motion?

Paul C
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Hey Cooking_Up_Code,

 

Unfortunately I do not have a scope here where the testing is being conducted. When I get back to my office, I will be able to test it, but unfortunately I am trying to do field testing this week. This accelerometer was purchased last month, so I highly doubt there is an issue with the accelerometer itself. I honestly think there may be issues with my 4 pin to BNC connector cable. Sadly I only have one cable on me right now, so I can't debug to see if this is the root of the issue.

 

What is strange is the Y and Z axes seem to react correctly and provide accurate G-loading data, but there seems to be a very low frequency drift where the voltage seems to oscillate. This drift is present even when the accelerometer is in motion. Not sure what would cause a voltage drift over time. Would this be caused by the excitation current oscillating?

 

Chris

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It does sound like it could potentially be an issue with a connection, so double checking it wouldn't hurt. Looking at your DAQ Assistant configuration, you are providing excitation on every axis, is this what your sensor requires? It may be that your Y and Z axes are being influenced by an unecessary excitation current.

Paul C
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