RESISTANCE TEMPERATURE DETECTORS (RTDs)
Temperature Detectors
RTD Construction
The RTD incorporates pure metals
Figure 1 Electrical Resistance-Temperature Curves
or certain alloys that increase in
resistance as temperature increases
and, conversely, decrease in
resistance
as
temperature
decreases. RTDs act somewhat
like an electrical transducer,
converting changes in temperature
to
voltage
signals
by
the
measurement of resistance. The
metals that are best suited for use
as RTD sensors are pure, of
uniform quality, stable within a
given range of temperature, and
able
to
give
reproducible
resistance-temperature
readings.
Only a few metals have the
properties necessary for use in
RTD elements.
RTD elements are normally constructed of platinum, copper, or nickel. These metals are best
suited for RTD applications because of their linear resistance-temperature characteristics (as
shown in Figure 1), their high coefficient of resistance, and their ability to withstand repeated
temperature cycles.
The coefficient of resistance is the change in resistance per degree change in temperature, usually
expressed as a percentage per degree of temperature. The material used must be capable of being
drawn into fine wire so that the element can be easily constructed.
IC-01
Page 2
Rev. 0
