Idiomas disponibles
Idiomas disponibles
4 Measurement Tutorials
Shielding
Shielding reduces the effect of common mode noise on a thermocouple measurement. Common mode noise is
generated by sources such as power lines and electrical motors. The noise is coupled to the unshielded
thermocouple wires through distributed capacitance. As the induced current flows to ground through the internal
DMM, voltage errors are generated along the distributed resistance of the thermocouple wire. Adding a shield to the
thermocouple wire will shunt the common mode noise to earth ground and preserve the measurement.
Common mode noise can dramatically affect the internal DMM. A typical thermocouple output is a few millivolts and
a few millivolts of common mode noise can overload the input to the internal DMM.
Calculation Error
An error is inherent in the way a thermocouple voltage is converted to a temperature. These calculation errors are
typically very small compared to the errors of the thermocouple, wiring connections, and reference junction.
Keysight DAQ970A/DAQ973A User's Guide
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