7. RESISTANCE TEMPERATURE DETECTORS
Resistance
Element
R1
R2
Vb
R3
RT
S
Bridge Output
Power
Supply
Resistance
Element
R1
R2
Vb
R3
RT
S
Bridge Output
Lead Resistance
Power
Supply
Resistance
Element
R1
R2
Vb
R3
RT
S
Bridge Output
Lead Resistance
Power
Supply
AND TABLE
63
A Resistance Temperature Detector (RTD) operates under the
principle that the electrical resistance of certain metals increa-
ses or decreases in a repeatable and predictable manner with a
temperature change.
RTD’s may have a lower temperature range than some thermo-
couples and a slower response time, however, they are more sta-
ble and repeatable over long periods of time. RTD’s higher signal
outputs make them easier to interface with computers & data
loggers. They reduce the effects of radio frequency interference.
RTD’s are used in: the plastic processing industry, environmen-
tal test chambers, motor windings, pumps and bearings, ovens,
kilns, waste treatment and the pulp & paper industry. RTD’s are
available in the same confgurations of thermocouples to suit
the most applications.
Basic RTD’s constructions
• Flat flm constructions, ceramic insulation
• Sealed biflar winding, ceramic insulation
• Sealed biflar winding, glass insulation
Standard wiring systems
RESISTANCE TEMPERATURE DETECTOR
2-wiring system
3-wiring system
4-wiring system