Continuous voltage output

[pdewey]

Hi,

I recently started using labview and was given a VI that included a custom built subVI that simply measures the voltage across a power resistor so that we can determine power consumed by a DC servo motor.  All I'm trying to do is obtain and record this voltage using a NI 6023e but am running into some trouble.  When the motor is turned on, instead of outputting instantaneous voltage the voltage slowly creeps up until it gets to 20V then it stops doing anything.  When I use a multi-meter to read the voltage it is actually hovering constant around ~0.3V, so what gives?

I've tried the subVI that I was given as well as a couple of examples included with the software and they all do the same thing.  I'm wondering if this is a grounding issue or possibly some setting isn't correct.  

Any help appreciated! 

[CWolf]

From what you are describing, it sounds like a grounding issue.  How do you have your voltage hooked up?  The pinouts for the device can be found in the User Manual.  If your task is set up for RSE measurement, then you will connect the positive voltage input to the AI pin and the negative to the AI GND pin.  If it is set up for NRSE measurements, then the negative will be connected to the AI SENSE pin.  If it is set up for differential measurements, then you will need to connect the positive lead to one of the AI 0-7 pins and the negative lead to the proper AI 8-15 channel.  (For example, for a differential measurement on AI 0, the positive will be connected to the AI 0 pin and the negative will be connected to the AI 8 pin.) 

-Christina