NI-9220 Voltage Measurement

[RichKnight]

I would like to use a NI-9220 to monitor the voltage of a test rig(12 21700 cells connected in series, each 4V, totally  around 50V).

When I setup the test rig and connected the rig with NI-9220, I found some channels were display wrong voltage(only 0.45v).

And then, I did a test, I connected the cell one by one, 1-5cells are good, when I connected 6/7 cells, the corresponding channel showed wrong voltage info.

Could I ask the reason?

BTW, I own 4 USB-6001 DAQ devices too, can I use them?

Kind Regards,

RichKnight. 

[ZYOng]

Can you provide the wiring diagram for when it worked and didn't work?

Is your signal source grounded? Have you tried adding bias resistors (see Field Wiring and Noise Considerations for Analog Signals)?

[RichKnight]

Hi ZYOng:

Thanks for your reply!

My signal source is not grounded, it just a battery pack. floating signal.

I could try the bias resistors next week, but I still have a question, I have 12 channels need to be measured, on the NI-9220, only exist 5 COM ports, should I add a bias resistor for each channel?

Kind Regards,

Francois