Question

The following transducer is used for accurate and precise measurement of temperature
1. Thermistor
2. Thermocouple (Alumel/Chromel)
3. Semiconductor temperature sensor chip
4. Platinum resistance thermometer

Answer 1

Correct Answer - Option 4 : Platinum resistance thermometer

Platinum Resistance Thermometer:

• A (PRT) is a piece of platinum wire which determines the temperature by measuring its electrical resistance.
• The electrical resistance of many metals (e.g. copper, silver, aluminium, platinum) increases approximately linearly with absolute temperature and this feature makes them useful as temperature sensors.
• The resistance of a wire of the material is measured by passing a current through it and measuring the voltage across it with a suitable voltmeter. The reading is converted to temperature using a calibration equation, and the PRTs work on this principle.
• It is used for accurate and precise measurement of temperature.

 

Important Points:

• The Thermistor is a solid-state temperature sensing device that acts a bit like an electrical resistor but is temperature-sensitive. Thermistors can be used to produce an analog output voltage with variations in ambient temperature and as such can be referred to as a transducer.
• A Thermocouple is a sensor used to measure temperature. Thermocouples consist of two wire legs made from different metals. The wires legs are welded together at one end, creating a junction. This junction is where the temperature is measured. When the junction experiences a change in temperature, a voltage is created.
• Semiconductor temperature sensors commonly use a bandgap element which measures variations in the forward voltage of a diode to determine temperature. To achieve reasonable accuracy, these are calibrated at a single temperature point, typically 25 °C.