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A millivoltmeter is used to measure EMF between a hot and cold junction of a thermocouple. The measurement can be directly graduated in temperature, if the temperature of...
  • A
    the hot junction adjusted to the standard temperature of 15°C.
  • B
    the hot junction and the cold junction are the same.
  • C
    the hot junction is kept constant.
  • D
    the cold junction is kept constant.

Refer to figure.
Temperature probes are formed from the junction of two dissimilar metals, when heated the junction generates a small voltage which is proportional to the actual temperature which produced it. The voltage can be measured on a millivoltmeter and displayed in the cockpit as the temperature at the rear of the engine.

The output from the probes is sent to the cockpit engine instrument, which is the cold junction, where the EMF is measured on a very sensitive milli-voltmeter to display the engine gas temperature.

A millivoltmeter measuring electromotive force between a hot and a cold junction of a thermocouple can be graduated to read temperature if the cold junction is maintained at a constant temperature.

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