Resistance Temperature Detector (RTD) (Temperature Transducer)

Principle

• A resistance temperature detector (RTD) can also be called a resistance thermometer as the temperature measurement will be a measure of the output resistance.
• RTDs are sensors used to measure temperature.
• The main principle of operation of an RTD is that when the temperature of an object increases or decreases, the resistance also increases or decreases proportionally.

Construction

• RTD act as variable resistor, when heat or temperature works on it.
• The figure 5.6 shows the RTD connected in the bridge arm as variable resistor.

Advantage

• Very stable output
• Linear and predictable
• Easy to verify and re calibrate
• High accuracy
• No special wire required for installation

Dis-advantage

• More limited temperature range (-200°C to 500°C)
• High initial price
• Slower response time than a thermocouple

Applications

• More Air conditioning and refrigeration servicing
• Air, gas and liquid temperature measurement
• Exhaust gas temperature measurement
• Food Processing
• Stoves and grills
• Textile production
• Plastics processing
• Petrochemical processing
• Micro electronics