NI 9220 maximum channel voltage parameters

[Boss-Hogg30]

Dear NI community,

I'm going to test a battery and I need to simultaneously acquire 6 cell's voltages (4.2V each) by cRio 9039 equipped with a NI 9220 . The battery consists of six cells voltages connected in series and directly measured by our NI 9220. Considering that we have connected every AI- input at the common with a 1MOhm resistance (p.14, GettingStarted), that's the question: in the NI 9220 datasheet is reported that the Maximum voltage (signal + common mode) must remain within +-10.4 V, what does it mean? how is it related to the the maximum 'Channel to COM' voltage (+- 30 V) reported in the NI9220 Getting Started Guide?

Thanking you in advance, i wish you a good day

[santo_13 · Accepted solution]

30V is overvoltage protection. You should never exceed +/-10.4V at either AI+ or AI- with respect to COM.

Overvoltage protection is there to protect the circuit in the event of a rare occurrence of a spike in the signal and not continuous operation.

For your application, since you connect the COM to -ve of a battery pack, the maximum you can measure cannot exceed 2 cells (as 3 cells will exceed the 10.4V limit).

Unless you add attenuators (resistor dividers) you cannot measure a 25V pack with an Analog input of range 20V (+/-10V).

[Boss-Hogg30]

Thank you santo_13 for your answer