Trouble with calibratet zero

[C-B]

Hi There,

I'm having some troubles with my SCXI 1520 device.

I'm using it with strain gauges. Chanel 0 in full bridge config, the other 7 are used as half bridges.

In MAX i have generated global virtual channels for each channel and put them into one task, where three more channels are configured.

These are voltage signals from a SCXI 1120 D

If I test the channels each one for it self I can calibrate it to zero, but if I put them into the task some of the channels do noz hit the zero line. As I'm using them to measure forces most of the channles are calibratet from -100N to 100N and show a zero line at about 15N.

Using the task in my VI the problem remains. If I seperate one channel from the task the zero line is correct. If I start all the channels together the results are wrong.

So I would really thank you for some ideas.

Message Edited by C-B on 03-01-2010 01:40 AM

[HoussamK]

Hi

which chassi are you using? Are you trying to configure the strain virtual channel  in the last three slots of your chassi?

If you are using the Traditional DAQ you can upgrade to NI-DAQmx and perform the calibration in a lower slot.

For more specific information please go to: Manual Strain-Null Calibration with File Output

[C-B]

I'm using a SCXI 1000 Chassis with SCXI 1600 Controller. As there are only thre ones behind the controller, the SCXI 1520 indeed is used on one of the last three slots.

In my VI I'm using DAQmx. I first tried the bridge calibration VI, but it didn't solve my problem.

But even in MAX it does not work properly. I tried to calibrate the virtual channels via MAX too, but with the same result: Individually activated the channels can be zeroed, but after putting them into the task the offset appears.

Thanks for your link, i'll give it a try, when I'm back to work tomorrow. Unfortunately I do not have any access to a Labview system now.

[HoussamK]

There are a number of workarounds:

Guidelines:

• 1. Open  MAX
  2. Power down the SCXI chassis.
  3. Move the module to a lower slot number.
  4. Power up the SCXI chassis.
  5. Go to the Properties of the Virtual Strain Channel in question.
  6. Select the current module slot.
  7. Perform the calibration 
  8. Power down the SCXI chassis.
  9. Move the SCXI module back to its original slot.
  10. Update the Virtual Channel to reflect the module's new slot.

You can use the SCXI calibration VIs in LabVIEW 😉

I hope this will help