Changing temperature measurements using USB 9211

[MEY]

I am using a USB-9211 to record 3 temperatures that are all connected to a waterbath that is set at 21C.  The recorded temps vary over time more than a degree or 2 each way with no apparent pattern.  There doesn't seem to be any reason for this. The water bath is calibrated and is accurate to +-.01C.  I tried using an ice bath with the same results. Do you have any idea what could be causing this variation?

Thanks,

[Elijah_K]

Hey MEY,

Have you consulted the user guide and specifications for the 9211 on our website?  Figures 9 through 13 demonstrate the error in degrees celsius for all the different types of thermocouples.  The user guide is available here: http://www.ni.com/pdf/manuals/371566c.pdf

What kind of thermocouple are you using?