|
| |
Back
The hot-wire movement | Up
Neets Module 03-Introduction to Circuit Protection, Control, and Measurement | Next
VOLTMETERS |
1-60
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.
|
