Thu18November0253AM 8

Regarding temperature measurement:

True / False

A thermistor has a metal oxide electrode whose resistance changes exponentially with increasing temperature Correct

A resistance thermometer is normally used in a Wheatstone bridge configuration Correct

The calibration of a thermistor is resistant to heat sterilisation Correct

Mercury thermometers are suitable for measuring temperatures from -30°C to at least +200°C Incorrect answer selected

A thermocouple relies on the Seebeck effect to measure temperature change Correct

Explanation

The mercury thermometer has a wide range from its melting point and is therefore suitable for measuring temperatures from -30°C to at least 200°C.

The resistance thermometer relies on linear change in the resistance of a platinum wire with temperature. Its sensitivity is improved by including it in a Wheatstone bridge.

The thermistor is a small metal oxide bead. Its resistance changes exponentially with a change in temperature. It is sensitive in the clinical range. Its calibration changes if it is subject to major changes in temperature that might be induced by heat sterilisation.

A thermocouple is a device that is used to measure temperature "electronically". It consists of a pair of dissimilar metal wires or strips bonded together, typically copper and constantan (an alloy of 55% copper and 45% nickel). When these wires contact each other a small voltage is generated in the order of millivolts. The magnitude of the thermojunction electromotive force (EMF) is proportional to applied temperature (the Seebeck effect). This physical principle can be applied to the measurement of temperature.

The electromotive force at the measuring junction is proportional to temperature.

Answer Statistics

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Average score: 65.94%

Times answered: 229