Principle

• A thermistor is a type of resistor whose resistance strongly depends on temperature.
• The word thermistor is a combination of word ‘thermal’ and ‘resistor’.

Construction

• Thermistors are generally composed of mixture of metallic oxides.
• The resistance of the thermistor is such that it vary with the thermal effect acting on it.
• When the thermistor gets heat, its resistance decreases and when it cools, its resistance increases.

Properties of Thermistor

• They have negative thermal coefficient. i.e. resistance of the thermistor decreases with increase in temperature.
• They are made up of the semiconductor materials.
• They are made sensitive than RTD and Thermocouples.
• Their resistance lie between 0.5Ω to 0.75 MΩ.
• They are generally used in applications where measurement range of temperature -60°C to 15°C.

• High sensitivity
• Can be used at normal room temperature
• High sensitivity
• Small size
• Low cost
• Fast response
• Simple conditioning circuit

• Non-linear
• High sensitivity allows the thermistor to work at low temperature range
• Not suitable for wide temperature change
• Shielded cable have to be used

• Applications include temperature measurements , compensation and control
• Used in air conditioners
• Used In detection of fire alarms

List of pressure transducers

• Strain gauge
• Capacitance type transducer
• Piezoelectric type transducer
• Optical type transducer
• Fibre-optic type transducer
• Surface acoustic wave type transducer
• Bridgeman type transducer
• Bourdon tube type transducer
• Diaphragm type transducer
• Bellows type transducer

List of pressure elements (pressure actuator)

• U-tube manometer
• Well type manometer
• Inclined manometer
• Diaphragms
• Capsule
• Bourdon tube
• Bellows