Definition
An electrical test instrument that measures very small voltages, expressed in millivolts (thousandths of a volt). In aircraft maintenance it is commonly used to read the low-level signals produced by thermocouples in cylinder head temperature and exhaust gas temperature systems.
Plain English
A meter that measures very tiny amounts of electrical pressure — the kind that are too small to register on a regular voltmeter.
Context Anchor
Seen in aircraft maintenance when checking small electrical signals in wires, sensors, or test equipment.
Derivation
Built from three parts: 'milli-' (Latin for one-thousandth), 'volt' (named after Alessandro Volta, the inventor of the battery), and 'meter' (Greek 'metron', meaning 'measure'). So literally: an instrument that measures thousandths of a volt.
Why Pilots Care
Correct millivolt readings confirm that temperature sensors deliver accurate data, which supports safe engine monitoring and prevents undetected overheating.
Intuition Check
A millivoltmeter does not measure a different kind of electricity; it measures the same thing as a voltmeter, but on a much smaller scale.
Example Sentence 1
The technician used a millivoltmeter to check the output of the cylinder head temperature thermocouple.
Example Sentence 2
A steady reading on the millivoltmeter during the engine run-up verified that the temperature indicator circuit was functioning properly.