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Which device is used to measure the temperature in the instrument?
Thermistor
Thermo couple
Thermo pies
None
Thermistor
Quick Summary: A thermistor is a type of resistor whose resistance is dependent on temperature, commonly used in measurement and control circuits. It acts as a passive transducer that converts thermal energy into a measurable electrical signal by changing its resistance value.
A thermistor is a type of resistor whose resistance is dependent on temperature, commonly used in measurement and control circuits. It acts as a passive transducer that converts thermal energy into a measurable electrical signal by changing its resistance value.
T1=A+Bln(R)+C(ln(R))3 — Steinhart-Hart equation relating temperature to resistance
RT=R0eβ(T1−T01) — Approximation formula using material constant β
The resistance R of a thermistor varies non-linearly with temperature T. This relationship is often modeled by the Steinhart-Hart equation: T1=A+Bln(R)+C(ln(R))3. When connected in a bridge circuit or a voltage divider, the temperature-induced change in resistance results in a measurable change in voltage.
Thermistors are classified as NTC (Negative Temperature Coefficient) or PTC (Positive Temperature Coefficient).
They offer high sensitivity and rapid response times compared to RTDs and thermocouples.
Used extensively in industrial temperature monitoring for electrical machines.
Very high sensitivity to small temperature changes
Low cost and compact physical size
Fast response time
Non-linear resistance-temperature characteristic
Limited operating temperature range compared to thermocouples
Prone to self-heating errors
Temperature measurement in electrical equipment
Overload protection circuits
Digital thermometers and thermostat controls
Option B (Thermocouple) generates a voltage based on the Seebeck effect, which is different from the resistance-based measurement of a thermistor.
Option C (Thermopiles) consist of multiple thermocouples connected in series or parallel to measure radiant heat.
A is correct — A thermistor is a highly sensitive semiconductor-based device that measures temperature by changing its electrical resistance.
Always remember that RTDs (Resistance Temperature Detectors) are generally linear, while Thermistors exhibit significant non-linearity which must be compensated for in software/circuitry.