Bad readings with SCXI 1125

[LinoR]

We are using Labview 6.0, NIDAQ 6.9.0f7, SCXI 1125 with SCXI 1327.

We are debugging a final testing equipment and noticed that randomly, it reads a 120V peak sine wave even if no voltage is applied at all. Applying a voltage of 220 rms, it still continues to read (and show) that 120V peak sinewave with no change at all.

The solution to exit from this situation is:

• either switch the equipment off and on again
• or test the board with the Measurement and Automation Explorer

This last solution does not work 100% of the times.

We downloaded the NI-DAQmx 8.0 but have some problems in installing it (the programm se a "nidaq32.dll" missing). 

Please help as our production needs the equipment in some days.

Many thanks.

[AlessioD]

I think a little more analysis should be done here:

• Has this equipment been working before?
• What is the DAQ board you are using to acquire from the SCXI chassis?
• what happens with the 1125 if you apply steady voltages?
• Could you post a screenshot of what you are seeing when acquiring?

NI-DAQ 6.9.0 is definitely way too old, I suggest you upgrade your Driver, but you should be aware of the following info.

As of version 7.0, NI-DAQ has been split into 2 families: NI-DAQmx and NI-DAQ Traditional. Basically the DAQmx driver is the new hw driver for new DAQ boards which offers enhanced performances.

Traditional NI-DAQ sets the continuity path with the Driver up to DAQ 6.9.3.

I suggest you try to download and install NI-DAQ Ver. 6.9.3, or, if you want to be up to date, you can install Trad NI-DAQ 7.4.1.

You can find all the drivers following this Web link .

Hope this helps,
AlessioD

[LinoR]

Alessio:

Thank for your reply. 

• Yes, the equipment has worked before
• The DAQ board is a PCI MIO16E4
• Applying steady voltages the 1125 and SCXI 1327 works OK, as actually when measuring 220V sinewave (from mains)

We have been actually diverted by another issue, beyond that explained at the beginning of this thread (that happens randomly and seldom). One channel with its gain set at 1, reads an apparent voltage (when it becomes very small) 100 times greater, showing 2-3 V instead than 20-30 mV or arount that value. Is there any way to avoid this apparent dinamically gain change?

Parallel to this analysis we have also downloaded the NIDAQ6.9.3 and will follow also this step, once completed the analysis and solved the above mentioned problem that does not allow us to go further.

Thank you again