Residual analog output from MSP C of myRIO-1900

[inquisitive27]

Hi everyone,

We have been using multiple myRIO-1900 for some of our projects in the lab. We use the MSP C port to send analog signals to an actuator's motion manager. Even without an instruction, a residual voltage (in tens of millivolts) exists at the analog output terminals. This creates an issue with the precise control of the actuator.

Here are a couple of questions in this regard:

1. Is this common -- due to the electrical tolerance, i.e., 1% of 10 V? 
2. Is there a way to overcome this? We could have added an offset to our code if the residual had been a constant. At times, it seems to vary with temperature. 

Any help in this regard is appreciated. Thanks in advance for your time!

[santo_13 · Accepted solution]

Your hardware is Academic grade and was not designed to be very precise and it is reflected in the specifications,

On the MSP connector, the absolute accuracy is +/-200mV

[santo_13]

Now, to the part about nulling out the offset/gain errors, you can add external OP-AMP circuits to adjust the offset and gain errors of the analog output and calibrate them against a DMM, but this is definitely a good chunk of work.

[RIObotics]

Hi there,

You can probably insert a relay switch in the middle of your analog output signal path.  You can use a DO line to toggle the switch, so that the AO path is disconnected, or tied to a known ground voltage, etc.  Or heck, you could use the switch to cut the power to your motors.  No power, no drift.  😁

BR

John

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