Receiving Analog signal using PXI 6143

[vicky2889]

Dear Sir,

I am new to PXI 6143 card. I am trying to receive the analog signal continuously. But the analog signal I receive is incrementing  and reach +5 V and stays at +5V. Same way when I connect the analog signal to -ai0 port first DAQ assist shows the value around -2.6v then starts decrementing and reach upto -5v and stay there. 

Please help me in this regard. How can I get the accurate value 

With Regards

VIKAS

[DJColeslaw]

Hi VIKAS,

When you have ai+ or ai- connected to the node you're trying to measure, what are you doing with the corresponding differential input line? It sounds like you're only connecting one side of the differential input which is incorrectly referencing the voltage you're measuring. You might have a look at this document. It has a table that shows correct physical configuration for differential connections to both grounded and ungrounded signal sources. Essentially, you want ai0 to be the high side of the differential signal you're measuring and ai- to be on the low side to make a meaningful differential measurement.

[vicky2889]

Hi Andrew,

Actually I am trying to receive a signal using PXI 6143 from chip that sending signal of around. 2.5 V. But in LabVIEW I am receiving voltage using DAQ assistant that starts incrementing and reaches to +5 V everytime. I dont understand why i am not getting the correct voltage of 2.5 V.

For checking I used function generator to generate a sine wave of amplitude 2 v but in this i am getting the incrementingg. Voltage everytime.

Please help. Me

Regards 

Vikas

[vicky2889]

Hi Andrew,

Please find the attached pics.

DAQ_assistant.JPG--- I used this way to receive the analog input signal using PXI 6143 but always incrementing the input signal and goes to +5V as even I set the Max voltage to +3V. 

DAQ2 --- I used this way to send the analog signal using PXI 6723 and receive analog signal using PXI 6143 but in this meter shows always +5V even I set the maximum voltage to +3V. 

Please help me in this. I never deal with analog signal using DAQ.

With Regards

[DJColeslaw]

Hi vicky2889,

As I mentioned in my previous post, it sounds like your problem is likely due to you physical configuration. Where are you connecting ai+ and ai- on the chip you're measuring? Can you send a picture or wiring diagram of you physical setup?

Also, especially in the case of express VIs like the DAQ Assistant, images aren't very useful. All of the configuration that would be useful to know hides inside the Express VI. Posting your actual code or VI Snippets is much more useful.

[vicky2889]

Dear Andrew,

I am not in the lab right now, so just drawing the connection diagram on the paper. 

Please find the attached picture.

I connect the analog signal to a0+ port using 68 pin of connector for DAQ PXI 6143 and used 67 pin of connector for gnd. I didn't used the a0-.

and I used the DAQVI VI for receiving the analog signal.

With Regards

VIKAS

[DJColeslaw · Accepted solution]

Vikas,

The documentation for 6143 Pinout says "Analog Input Ground—These terminals are the bias current return point for AI DIFF measurements" which sounds like a place to attach something like a shield to sink current but won't actually make a valid differential measurement. To get a good measurement, you'll want your chip high output tied to ai+ and chip low output tied to ai-. I think that extra ground pin just lets you tie in a shield and sink current into that pin without adding noise onto one of the differential lines, which would ruin the noise susceptibility improvement of using a differential measurement device.

[vicky2889]

Hi Andrew,

I am confused in a0+ a0-. 

I have only two wires one for signal line and other is ground. I checked this signal using oscilloscope its showing correct value of 2.5 v. But when i am checking with daq i am not getting.

Can you please show me an example like using function generator (also having two wires one for signal and other for ground) so that i can understand how to connect the two wires to DAQ card pins correctly.

[vicky2889]

thank you andrew,

I was confused between two gnd.

Now I am getting signals very fine.

With Regards

VIKAS