PXI-6704 AO Voltage Spike during Power Down

[griplegraple]

Current Setup: PXI 6704 connected to SCB68A. On one of the analog outputs, I have a motor (powered via 24 VDC and controlled by 0-5V via PXI 6704).

 During power up (powering up the PXI chassis), 0 volts are shown from the 0-5 V ouput. When I shutdown (i.e. turn off 24 VDC power supply and PXI Chassis, a 3.64 Volt spike develops at the 0-5V output and the motor spins then shuts down as the powersupply is also shut off during this time.

I tried leaving the AO ground open and also grounded to the 24 VDC common. Both result in the same issue.

Any ideas on how to fix this?

Thanks for the help.

[Rairiki]

Hello 

So you have a power spike after you shut down the PXI chassis and this spike goes off after you shut dow the power supply?

Regards

[griplegraple]

The chassis is still powered on when the voltage spike develops. This spike occurs when the power supply (24 VDC) is turned off/ disconnected prior to turning off the chassis.

As a current fix, I connected the 0-5 AO from the 6704 to a relay and I keep the relay in the "open state" during power off. Even if the spike develops, no connection to the motor is made.