Definition
An instrument that measures electrical current by sensing the heat produced when that current flows through a fine resistance wire. The wire's expansion or the temperature rise at a thermocouple junction is converted into a meter reading calibrated in amperes. Because it responds to heating effect rather than to the direction of current flow, a thermoammeter reads both direct current and alternating current, including the high-frequency current found in radio transmitter antenna circuits.
Plain English
A meter that measures how much electricity is flowing by measuring how hot the flow makes a small wire. It works for both regular DC current and AC current, including the kind used in radios.
Context Anchor
Seen mainly in aircraft electrical system maintenance and older instrument or radio equipment discussions.
Derivation
Built from 'thermo-' (Greek for heat) and 'ammeter' (an instrument that measures amperes). The name describes exactly how it works: it measures current by measuring heat.
Why Pilots Care
On aircraft equipped with one, a thermoammeter on the transmitter panel confirms that radio energy is actually reaching the antenna. A low or zero reading during transmission can indicate a broken antenna lead or a failing transmitter.
Intuition Check
Do not read thermoammeter as a thermometer. It does not measure outside temperature; it measures electric current by using heat inside the instrument.
Example Sentence 1
The pilot watched the thermoammeter swing upward as he keyed the microphone, confirming the transmitter was sending power to the antenna.
Example Sentence 2
During the electrical inspection, the thermoammeter needle stayed within the normal range.