Re : 6251 analog output 100 uV jumps

[alegadda]

Hi, I have a problem with the analog output voltage of a BNC 6251 DAQ. When I try to output relatively small voltage signals (e.g.1 mV) I can measure strange, infrequent jumps of the output about 100 microvolts high. After a few seconds (sometimes less, sometimes more), the output usually reverts to the original value. This does not depend on the output range, i.e. 10 V or 5 V; moreover, I get this also using an external reference for the DAC set down to 100 mV, so it is not simply a quantization problem. The external reference is a very stable DC voltage source. I am using the inputs of the board itself to measure this, but it is not an input problem i.e. I can measure just fine other signal sources. I'm using a simple Labview code, but it does not seem a software problem: the signal values fed to the subVIs are correct. I tried both with the DAQ assistant and the single DAQ Mx subVIs (for the external reference). Any ideas? Thanks!

[JérémyC]

Hello alegadda,

I'm not sure about the aspect of the jumps you described but maybe, you're talking of the glitches which are expected behavior :

Reducing Glitches on the Analog Output of MIO DAQ Devices

If it doesn't fit with what you see, maybe this is noise that comes from the device you use to measure the output voltage. It may also come from a bad calibration of the device.

Regards,

[alegadda]

Thanks, but it's not a short voltage spike. It is more of a two-state transition, e.g. the voltage would suddenly increase of 100 uV and come back down after, for example, ten seconds. It is not a measuring problem, I am using the board itself to monitor the output and I have no problem with voltage outputs from other devices. I am starting to think it is really a calibration problem.