MyRio MSP connector question

[MinFah]

Hello all,

Is it possible to connect the MSP Connector AI0-  and AGND together as ground?  I understand that it should not be done as the input is a differential input.

Found out that it I do that, I get the perfect sine curve with the correct voltage in my Labview program.  attaching only AI0-, I do not get a perfect curve. 

Regards

MinFah

[MrJacket]

Hey,

Have you tried doing the signal as single-ended? That is what it sounds like you are doing. Or does it have to be differential?

Thanks,

-Brian J. 

[charlesy · Accepted solution]

Hello MinFah,

Yes, it's OK to connect MSP AI0- to AGND. The analog inputs on the MSP connector are differential, which means they measure the difference between the '+' and '-' terminals. Those terminals can be anything between about -10V and +10V, so AGND (0V) is fine.

Now, as to whether that's the right connection to make for your measurement, depends on the circuit. I assume you are generating a sine wave on the analog output (AO0) and want to measure it back with the analog input (AI0). See attached diagram. While the MSP Analog Inputs are differential (measuring between '+' and '-'), the MSP Analog Outputs are single-ended. This means that the output voltage on AO0 is generated with respect to AGND. If you want to measure it, you need to probe between AO0 and AGND. Use AI0+ and AI0- to measure the difference between those two points.

I hope this is helpful. Good luck!

Charles Y.

National Instruments

[MinFah]

Charles, 

thanks that is what I wanted to do.