NI9217 sharing same signal on multiple channels

[Bor0x]

Hi All, 

I have to create a VI that performs several tests on a PT100, I'm using an NI9217 mounted on an NI cDAQ 9174.

The VI has to perform one 4 Wires test and two 2 Wires test. The problem comes when I have to make a bridge between 2 channels to use on both the same signal, It always gives me totally wrong values, I tried to see similiar thread but I didn't find any possible solution. 

If there is anything else you may need to know to help please ask.

Thanks in advance for your help.

[rolfk]

It's not quite clear what exactly you try to do. All the channels on the 9217 share a common ground so if the reference potential between the channels is not the same or not fully isolated, you for sure will get trouble if you try to connect multiple channels somehow.

[GerdW]

Hi Bor,

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@Bor0x wrote:

The problem comes when I have to make a bridge between 2 channels to use on both the same signal, It always gives me totally wrong values,

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That's usually not possible with RTD sensors like your Pt100!

Both channels try to drive a current through your resistor and so they interfere with each other!

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@Bor0x wrote:

The VI has to perform one 4 Wires test and two 2 Wires test.

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The NI9217 only supports 4-wire and 3-wire configurations…

(Reading the manual often helps when having problems with your hardware!)