USB-6211 Analog output won't go below 3.38V

[Jeff_Gu3]

Hello

I am using a USB-6211 board that needs to output a variable voltage to control a high voltage power supply. It was working fine previously, but now the voltage of both ao0 and ao1 won't go below 3.38V (which translates to ~10kV on my high voltage power supply). It jumps up as soon as I plug in the USB cable regardless of whether LabView is running or not. I need this to go back to zero, but nothing I have tried has helped. I've tried resetting the device using the Measurement and Automation explorer, restarting the computer, unplugging the device, and reprogramming the ao control in LabView. I've unplugged everything from the 6211. Any help would be appreciated.

Thanks

Jeff

[JaymeW]

Hi Jeff,

Have you tried changing the voltage output in a Measurement & Automation Test Panel and measuring it with a voltmeter or multimeter? 

[Jeff_Gu3]

Hi Jayme

Thanks for your reply. I tried what you suggested and I have the same problem. It works fine above 3.38V for both chanels, but if I set the voltage to anything below that, it still reads 3.38V. I also tried a self test that passed, and a self calibration and that failed.

Jeff

[SnowMule]

Sounds like your daq's broken.... time for a new one, or ship it back to NI for repair.

[AnalogKid2DigitalMan]

What is the make/model of the Hi V supply?

Many I have dealt with before specifically call out the need for electrical isolation on the analog control inputs. This is to protect the voltage source from any leakage and/or ground loops.

You may want to check tha manual of the supply if isolation is needed.

-AK2DM

[Jeff_Gu3]

Hi AK2DM

It's a Spellamd CZE 1000. The manual doesn't say anything about electrical isolation.

Thanks

Jeff

[AnalogKid2DigitalMan]

Jeff:

On page 17 it does call out that isolation is preferred:

3.2 Standard Features

A note on remote interface circuitry and remote signal

grounding: whenever possible, electrical isolation should

be provided when interfacing with any high voltage power

supply. For enable/disable signal connections, an isolated

relay or optocoupler should be used. If possible, analog

programming and monitoring signals should be isolated

via analog isolation amplifiers. Spellman application

engineers are available to assist in interface circuitry

design. All interface cables should be properly shielded.

All power supply signals should be referenced to the

power supplies signal ground or power supply chassis

ground.

-AK2DM

[Jeff_Gu3]

Hi AK2DM

It seems I can't spell. I meant Spellman CZE 1000R. I checked your reference because there isn't a page 17 in the 1000R manual, and you were quoting from an SL series power supply as far as I can tell. Unless I'm missing something, I still dont see any documentation stating that electrical isolation is recommended for my PS.

Thanks

Jeff

[AnalogKid2DigitalMan]

Jeff:

Yes, I must have been looking at another series. Regardless, it sounds like the DAQ is damaged. Personally, I use some form of isolation whenever the system voltages involved (or potentially be involved if something fails) exceeds 50V.

-AK2DM

[rfgarciar]

Hi,

I have exactly the same problem. Do you know the solution?

I did not apply voltages higher than 10V.