Hi MaxiMuz1979,
Here is the point of contact for National Instruments Calibration services: http://www.ni.com/services/calibration/
The accuracy of the electronic components used in all instruments drift some amount over time. The effects of time in service as well as environmental conditions add to this drift. As time progresses, changes in component values cause greater uncertainty in your measurements. After a year, it is recommmended to check these devices for calibration.
For more information on the calibration and maintenance of these PXI chassis and Modules, please refer to this link, specifically Point 4.7: http://www.ni.com/white-paper/5822/en/#toc4
Thanks.
