Analog Out PXI-7342 w/ UMI-7764 - floats when chassis not on - pull-down?

[RVallieu]

The analog output from the PXI-7342 connected to UMI-7764 floats to some non-zero Voltage when the chassis is not powered.

Is it safe to add a pull-down resistor to the analog output to ground to prevent this?

The axis that is connected will try to move the motor when it sees the floating signal.

[Jochen]

The analog outputs on the 7342 can source up to 5 mA. With this current the voltage drop is about 0.5 V (e. g. 9.5 V instead of 10 V). So yes, you can tie the output to GND with a pull-down resistor, but you shouldn't use very low resistor values. The resulting resistance of the the pull-down resistor and the input impedance of your drive shouldn't be lower than 2 kOhm.

Regards,

Jochen Klier
National Instruments

[RVallieu]

Thanks for the fast response!

[RVallieu]

I ended up using a 2.2 kOhm resistor.  Worked like a charm.