©National Instruments Corporation5-1PCI-MIO E Series User ManualChapter5CalibrationThis chapter discusses the calibration procedures for yourPCI-MIO E Series board. If you are using the NI-DAQ device driver,that software includes calibration functions for performing all of thesteps in the calibration process.Calibration refers to the process of minimizing measurement and outputvoltage errors by making small circuit adjustments. On thePCI-MIO E Series boards, these adjustments take the form of writingvalues to onboard calibration 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, whereasthe last level is the slowest, most difficult, and most accurate.Loading Calibration ConstantsYour PCI-MIO E Series 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, youmust 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.
