©National Instruments Corporation5-1PCI-6110E/6111E User ManualChapter5CalibrationThis chapter discusses the calibration procedures for your 611X Eboard. If you are using the NI-DAQ device driver, that softwareincludes calibration functions for performing all of the steps in thecalibration process.Calibration refers to the process of minimizing measurement and outputvoltage errors by making small circuit adjustments. On the 611X Eboard, these adjustments take the form of writing values to onboardcalibration DACs (CalDACs).Some form of board calibration is required for all but the most forgivingapplications. If you do not calibrate your board, your signals andmeasurements could have very large offset, gain, and linearity errors.Three levels of calibration are available to you and described in thischapter. The first level is the fastest, easiest, and least accurate;whereas, the last level is the slowest, most difficult, and most accurate.Loading Calibration ConstantsThe 611X E board is factory calibrated before shipment atapproximately 25° C to the levels indicated in Appendix A,Specifications. The associated calibration constants—the values thatwere written to the CalDACs to achieve calibration in the factory—arestored in the onboard nonvolatile memory (EEPROM). Because theCalDACs have no memory capability, they do not retain calibrationinformation when the board is unpowered. Loading calibrationconstants refers to the process of loading the CalDACs with the valuesstored in the EEPROM. NI-DAQ software determines when this isnecessary and does it automatically. If you are not using NI-DAQ,you must load these values yourself.In the EEPROM there is a user-modifiable calibration area in additionto the permanent factory calibration area. This means that you can loadthe CalDACs with values either from the original factory calibration orfrom a calibration that you subsequently performed.