Some electrical and electronic devices have meters built into them. These meters are known as in-
circuit meters. An in-circuit meter is used to monitor the operation of the device in which it is installed.
Some examples of in-circuit meters are the generator or alternator meter on some automobiles; the
voltage, current, and frequency meters on control panels at electrical power plants; and the electrical
power meter that records the amount of electricity used in a building.
It is not practical to install an in-circuit meter in every circuit. However, it is possible to install an in-
circuit meter in each critical or representative circuit to monitor the operation of a piece of electrical
equipment. A mere glance at or scan of the in-circuit meters on a control board is often sufficient to tell if
the equipment is working properly.
While an in-circuit meter will indicate that an electrical device is not functioning properly, the cause
of the malfunction is determined by troubleshooting. Troubleshooting is the process of locating and
repairing faults in equipment after they have occurred. Since troubleshooting is covered elsewhere in this
training series, it will be mentioned here only as it applies to circuit measurement.
In troubleshooting, it is usually necessary to use a meter that can be connected to the electrical or
electronic equipment at various testing points and may be moved from one piece of equipment to another.
These meters are generally portable and self-contained, and are known as out-of-circuit meters.
Out-of-circuit meters are more versatile than in-circuit meters in that the out-of-circuit meter can be
used wherever you wish to connect it. Therefore, the out-of-circuit meter is more valuable in locating the
cause of a malfunction in a device.
Q1. What are two ways that circuit measurement is used?
Q2. Why are in-circuit meters used?
Q3. What is one advantage of an out-of-circuit meter when it is compared with an in-circuit meter?
BASIC METER MOVEMENTS
The meter movement is, as the name implies, the part of a meter that moves. A meter movement
converts electrical energy into mechanical energy. There are many different types of meter movements.
The first one you will learn about is based upon a principle with which you are already familiar. That
principle is the interaction of magnetic fields.
COMPASS AND CONDUCTING WIRE
You know that an electrical conductor in which current flows has a magnetic field generated around
it. If a compass is placed close to the conductor, the compass will react to that magnetic field (fig. 1-2).