Voltage measurement not proper on NI9201

[Rohit3453]

I made a simple program to measure DC Voltage using DAQ Assist. The problem i am facing is that when i connect no power supply to DAQ it is not showing 0 voltage and it is fluctuating due to which I am not able to take proper readings

[GerdW]

Hi Rohit,

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@Rohit3453 wrote:

The problem i am facing is that when i connect no power supply to DAQ it is not showing 0 voltage and it is fluctuating due to which I am not able to take proper readings

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The NI9201 module doesn't require any external power supply (supply on its own): what are you talking about?

(Ofcourse you need to power the chassis where the NI9201 is plugged in!)

When the chassis is not powered then you should get a DAQmx error…

You can make "proper readings" even when the readings are fluctuating!

[Rohit3453]

Hii thanks for replying 

i was talking about the voltage values measured by the module. I wanted to measure voltage of a device but when I ran the program without connected any device. The program was not showing 0 voltage and it varied highly 

[LVIEWPQ]

What are you reading in NI max with nothing connected? 

Sounds like dodgy grounding or ghosting. 

[JÞB]

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@Rohit3453 wrote:

I made a simple program to measure DC Voltage using DAQ Assist. The problem i am facing is that when i connect no power supply to DAQ it is not showing 0 voltage and it is fluctuating due to which I am not able to take proper readings

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What is the input configuration?  I suspect that you have set to NRSE (non-referenced single ended).  With neither signal source nor reference connected,  what you describe would be expected.  What happens when you read a RSE measurement or connect the reference to ground?

[ZYOng]

NI does not specify what voltage a device will read when there is no signal connected.

Reference: Incorrect Readings on Unconnected or Open Channels of DAQ Device