Definition
An electrical instrument that measures the power, in watts, being consumed by a circuit or delivered to a load. It senses both voltage and current simultaneously and indicates the product of the two, accounting for any phase difference between them in alternating-current circuits.
Plain English
A meter that shows how much electrical power something is using or producing, measured in watts.
Context Anchor
Seen in aircraft electrical-system testing, maintenance, and discussions of how much power lights, radios, or other equipment use.
Derivation
Combines watt (the unit of electrical power, named after Scottish engineer James Watt) with meter (a device that measures). The watt itself is defined as one joule per second, or one volt multiplied by one ampere in a direct-current circuit.
Why Pilots Care
Confirms that generators, alternators, and batteries are supplying the correct amount of power to flight-critical systems.
Intuition Check
A wattmeter does not just show that electricity is present. It shows how much electrical power is actually being used or delivered.
Example Sentence 1
The technician connected a wattmeter to the inverter output to verify it was delivering its rated power.
Example Sentence 2
During an electrical inspection the technician watched the wattmeter to ensure battery drain stayed within limits.