problem - when we start/stop big DC var speed motor nearby, cRIO locks up

[TAB Tomb]

cRIO is in a grounded stainless steel enclosure.  It is powered by power supply in same enclosure.  Power and signal grounds are tied at single point with large guage wire to earth.

[jpaul]

Hi TAB Tomb,

Is the cRIO's power supply at all dependent on the same power grid as the DC motor? Can you monitor whether the cRIO is receiving enough power when this motor is started/stopped? In addition, what cRIO and chassis are you using?

Cheers,

Jonah
Applications Engineer
National Instruments

[TAB Tomb]

the cRIO power should be independent, but I have yet to verify this.  I will be on-site Monday and will have additional verification of power and wiring.  I plan to monitor during motor start / stop, I can be assured of catching brown outs, etc. however catching induced spikes is usually more difficult and I am less confident of catching these if present.  The instrument wiring goes to the compressor that the motor is driving, so it is in moderately close proximity to the motor and it's power wiring.  I will have only limited number of starts-stops to monitor each day (two or so) which adds to the difficulty of catching transients. 

I am using the cRIO 9012 RT processor and the 9102 8 slot chassis.  The vi's are very simple (triggered, medium-speed data sampling, with some post acquisition processing) however the RT VI does invove writing files of data to disk, periodic ftp transfer of these files and occasional remote ethernet display of the RT vi front panel.

[jpaul]

TAB Tomb,

Please let me know the outcome of your testing today and we can proceed from there. The link below is to the power specifications (Pg. 15) for the cRIO-9012 as a reference to ensure that the minimum values are being met. Another option to try is to wire up the second power terminal to a power supply that is farther away (or less dependent on the motor circuit) if possible, because although the cRIO does not draw from both power supplies, it may ensure a second source if the first goes down during the motor initialization.

cRIO-9012 Specifications

Thanks,

Jonah Paul
Applications Engineer
National Instruments