Calibration Circuitry; Signal Conditioning; Sensors And Transducers - National Instruments NI 6221 User Manual

Calibration Circuitry

Signal Conditioning

Sensors and Transducers

© National Instruments Corporation
The M Series analog inputs and outputs have calibration circuitry to correct
gain and offset errors. You can calibrate the device to minimize AI and AO
errors caused by time and temperature drift at run time. No external
circuitry is necessary; an internal reference ensures high accuracy and
stability over time and temperature changes.
Factory-calibration constants are permanently stored in an onboard
EEPROM and cannot be modified. When you self-calibrate the device,
software stores new constants in a user-modifiable section of the EEPROM.
To return a device to its initial factory calibration settings, software can
copy the factory-calibration constants to the user-modifiable section of the
EEPROM. Refer to the NI-DAQmx Help or the LabVIEW Help in version
8.0 or later for more information about using calibration constants.
For a detailed calibration procedure for M Series devices, refer to the
B/E/M/S Series Calibration Procedure for NI-DAQmx by clicking Manual
Calibration Procedures on
Many sensors and transducers require signal conditioning before a
measurement system can effectively and accurately acquire the signal. The
front-end signal conditioning system can include functions such as signal
amplification, attenuation, filtering, electrical isolation, simultaneous
sampling, and multiplexing. In addition, many transducers require
excitation currents or voltages, bridge completion, linearization, or high
amplification for proper and accurate operation. Therefore, most
computer-based measurement systems include some form of signal
conditioning in addition to plug-in data acquisition DAQ devices.
Sensors can generate electrical signals to measure physical phenomena,
such as temperature, force, sound, or light. Some commonly used sensors
are strain gauges, thermocouples, thermistors, angular encoders, linear
encoders, and resistance temperature detectors (RTDs).
To measure signals from these various transducers, you must convert them
into a form that a DAQ device can accept. For example, the output voltage
of most thermocouples is very small and susceptible to noise. Therefore,
you may need to amplify or filter the thermocouple output before digitizing
ni.com/calibration
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Chapter 2 DAQ System Overview
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M Series User Manual