National Instruments NI 5911 User Manual

Also see for NI 5911: Getting started guide

Contents

National Instruments NI 5911 User Manual Manual pdf 18 page image

Chapter 2 Hardware Overview© National Instruments Corporation 2-7 NI 5911 User ManualCalibrationThe NI 5911 can be calibrated for very high accuracy and resolution dueto an advanced calibration scheme. There are two different types ofcalibration: internal, or self, calibration and external calibration. A thirdoption, internal restore, restores factory settings and should be used only inthe event of a self-calibration failure.Internal calibration is performed via a software command thatcompensates for drifts caused by environmental temperature changes. Youcan internally calibrate your NI 5911 without any external equipmentconnected. External calibration recalibrates the device when the specifiedcalibration interval has expired. See Appendix A, Specifications, for thecalibration interval. External calibration requires you to connect an externalprecision voltage reference to the device.Internally Calibrating the NI 5911Internally calibrate your NI 5911 with a software function or aLabVIEW VI. See Chapter 3, Common Functions and Examples, of yourNI-SCOPE Software User Manual for step-by-step instructions forcalibrating your digitizer.When Internal Calibration Is NeededTo provide the maximum accuracy independent of temperature changes,the NI 5911 contains a heater that stabilizes the temperature of the mostsensitive circuitries on the board. However, the heater can accommodatefor temperature changes over a fixed range of ±5 °C. When temperaturesexceed this range, the heater no longer is able to stabilize the temperature,and signal data becomes inaccurate. When the temperature range has beenexceeded, you receive a warning, and you need to perform an internalcalibration.What Internal Calibration DoesInternal calibration performs the following operations:• The heater is set to regulate over a range of temperatures centered atthe current environmental temperature. The circuit components requirea certain amount of time to stabilize at the new temperature. Thistemperature stabilization accounts for the majority of the calibrationtime.• Gain and offset are calibrated for each individual input range.