cDAQ 9220 input voltage range?

[roger1922]

We have just bought some compactDAQ systems with NI 9220 voltage input modules.

If I run NI Max, the test panel has controls for a "maximum input limit" and a "minimum input limit", as has  DAQmx Create Channel (AI-Voltage-Basic).vi.  This implies that one could, for instance, set the range as -1 to +1, or 0 to 0.2 volts, or even -0.001 to +0.001 volts.

What do these actually do?  Do they configure the gain and offset of an analogue amplifier in front of the A/D or do they simply perform some software clipping of voltages that exceed these limits?   The specification for the 9220 is that its range is +/- 10 volts, which seems to imply that it is not user-configurable.  Conversely the 9220 datasheet 378023a.pdf says that the measurement voltage (AI- to AI+) is minimum +/- 10.4 volts, typical +/- 10.5, max +/- 10.6 volts, which implies that even setting +/-10 might not be allowed.

[AJost · Accepted solution]

Hi Roger,

The Testpanels are universal for all DAQ modules, so they indeed offer some functionality which are not very useful for the 9220.

For some modules, changing the input limits will automatically adjust the gain of the amplifier. As the 9220 only has a fixed gain, it will just clip the data if you put a lower range.

So the +-10 Volt is certainly allowed and is what I would recommend.

The extra 0.xV is more of a safety margin if you need to calibrate the module (if you calibrate you are shifting around the range)

Andreas

[roger1922]

Hi Andreas

Thanks, that's helpful.

Roger