NI-9253 no current read

[Jobar1933]

Hi all,

I have issues with the NI-9253 module and a pressure sensor. My pressure sensor has 2 wires (+ and -) and I have tried connecting them to the NI-9253 but all the reading I get is almost 0 (basically the same as using a channel where the sensor isn't connected).

I have connected my sensor + to Vsup and my sensor - to AI0, and I have adjusted the min and max values to be 4mA and 20mA respectively. I read that the NI-9253 has got internal power supply.

What am I doing wrong?

Best regards,

MAtt.

[cfy2020 · Accepted solution]

Hi,

The NI-9253 itself does not have internal power supply to supply power to the sensor. You need to connect an external power supply to the Vsup and COM pins of the NI 9253 in order for it to supply the power to you sensor, as indicated in page 8 of the NI 9253 Getting Started Guide. Hope that helps.

[Jobar1933]

I did as you said and yes it works. I've read here but didn't fully understand the answer which in hindsight was clear. My bad (https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000g2S1SAI&l=fr-CH). Problem solved!

[Jobar1933]

I do have an additional question tho. I have a sensor that has a "signal" output wire and its own power supply. When I am measuring current between this output wire and the sensor ground using an ampere meter I am getting the current it should. But how should I connect this signal output pin to the NI-9253? I've tried in an AI but I'm not getting anything.

If I am understanding things right that sensor is "single ended" so I cannot connect it to the NI-9253? Can I "convert" it to differential so I can connect it to the NI-9253 that has already other differential sensors output connected?

[cfy2020 · Accepted solution]

Since your sensor already has the power supply, you do not need to connect your sensor to the Vsup terminal on the NI 9253. Have you tried connecting the sensor's "signal" output wire to the AI terminal on the NI 9253, and the sensor ground to the COM on the NI 9253? You should be able to measure something there.

[Jobar1933]

Fantastic it works! I was afraid to connect the ground as I thought it would interfere with the external power supply I had connected to the NI-9253. Thank you!