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The thermocouple movement uses the current being developed in a thermocouple when the heat of a
resistive wire is transferred to the thermocouple. The developed current is measured by a very sensitive dc
ammeter. This movement will measure only current.
An AMMETER measures current. It is always connected in series with the circuit being measured.
An ammeter should have a small resistance so the effect of the ammeter on the circuit will be kept to a
minimum. Ammeter sensitivity is the amount of current that causes 0 full scale deflection of the ammeter.
Shunt F resistors are used to provide an ammeter’s ranges.
The following SAFETY PRECAUTIONS should be observed when using an ammeter.
Always connect an ammeter in series.
Always start with the highest range.
Deenergize and discharge the circuit before connecting or disconnecting an ammeter.
Never use a dc ammeter to measure ac.
In dc ammeters, observe the proper polarity.
