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Voltage Measurement with Multiple Devices in Parallel

Hi all,

 

I am using a transducer with a 0-10 V analog output signal that is acting as a feedback signal to a stand-alone external PID module. I would also like to monitor the transducer feedback signal simultaneously using an NI DAQ and LabVIEW. My hardware is the PCI-6221 with BNC-2120 breakout. I am using a differential analog input.

 

When connecting the transducer to each of the DAQ and PID module independently, I get a correct 0-10 V measurement. When connecting to both the DAQ and PID module simultaneously, I am seeing a 0-~3.5 V measurement.

 

The PID module datasheet lists an impedance on its feedback terminal as 100 kohm, while the 6221 lists an impedance as > 10 Gohm. My initial reaction (and after some Google-ing) is the massive impedance mismatch is preventing me from splicing the signal properly and I likely need a buffer amplifier. Have folks encountered this problem before? If so, is there something else I should be considering?

 

Any input (pun intended) is appreciated!

 

Eric

 

 

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