Analog input to PCI-6229

[zacharia01]

Hello forum,

I have been trying to acquire the analog input voltage signal from a pressure transducer using PCI6229+SCB68. The transducer is powered by a AC/DC adaptor. I assume that the signal comes out of the transducer is floating signal as the transducer is not explicitiy connected to the wall plug. I tired to acquired the signal using Single Ended Grounded Referenced by connecting to AI 0 and AIGND. I did not read the right voltage, always show -10.7 V. Then I chose to go for DIFF mode, where I connected the signal AI0 and  AI8. The same response. I am not clear if the signal I am having is floating or not? Can you tell me, how I can determine as I am not connecting the device explicitly to the wall plug. Also, please tell me how I can acquire this signal using the PCI6229. In the Field Wiring App note, it is mentioned that bias resistors must be provided when measuring the floating signal using DIFF or NRSE configs. Is that the way I should do ?

Many thanks in advance,

Zch

[P.Sanders]

If the signal source is floating, use differential mode. The following document should shed some light on where to place bias resistors and correctly read analog signals!

[zacharia01]

The link did not work unfortunately. Right now, I followed the instructions in the field wiring application note and used DIFF mode for floating signal source. Consequently, I could get the signals.

Thank you.

[P.Sanders]

For future reference: https://www.ni.com/en/shop/data-acquisition/measurement-fundamentals/field-wiring-and-noise-consider...

😉