RTD Measurement

Saturday, November 18th, 2017 - Passive Transducers, Resistive Transducers, Temperature

RTD Measurement

The electrical resistance of a metal conductor increases as temperature increases. This is because the electrical conductivity of a metal relies on the movement of electrons through its crystal lattice. Due to thermal excitation, the vibration of electrons increases, which slows the electrons’ movement, thus causing the resistance to increase.

The temperature coefficient of an alloy is often very different from that of the constituent metals. Small traces of impurities can greatly change the temperature coefficients.

An RTD is a passive device, requiring a current to pass through to produce a measurable voltage. If the excitation current passing through an RTD is Iex, and the output voltage across the RTD is Vout, then the measured temperature T (in °C) can be obtained by.

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RTDs can be difficult to measure due to their relatively low resistance (e.g., 100 Ω), which changes only slightly with temperature (<0.4 Ω ⋅ °C−1). To accurately measure these small changes in resistance, special configurations should be used to minimize errors from lead wire resistance.

I hope this information about “RTD Measurement” is useful.