usb-6211 offset

[semdevelopment]

Hello,

I just received a new USB-6211 device which shows approx. -3 mV (constant) offset for all input channels when the corresponding connectors (measuring the difference between two connectors) are short-circuited with a short wire. After self-calibration this offset goes down to a few µeV for something like 10 seconds. After this, it increases within approx. 3 seconds until is stabelized around -3 mV.

Is this a normal "feature" of the USB-6211 or is anything wrong with our one?

Since we would like to measure voltages in the mV range and thermovoltages, we would really like to get rid of this.

Thank you very much for any kind of help!

Kai

Message Edited by semdevelopment on 01-17-2008 06:31 AM

[JoBa]

Hello Kai,

the specifications for the USB-6211 show an accuracy of 2.69 mV for the 10 V range, so the offset of approximately 3 mV of your device might still be inside the specs.

Does the offset change when you switch to another input range, e.g. -1 to 1 V?

Best Regards,
Johannes

NI Germany         624036