# Electrical Measurements

The field of electricity, accurate quantitative measurements are essential. A technician commonly works with current, voltage , and resistance.
Ammeters, voltmeters, and ohmmeters are used to provide the essential measurements. A good understanding of the design and operation of electrical measuring meters is important.

## INTRODUCTION TO METERS

Meters are the means by which the invisible action of electrons can be detected and measured. Meters are indispensable in examining the operation of a circuit.
Two types of meters are available. One typeÂ is the analog meter, which uses a graduated scale with a pointer . The other type is theÂ  digital meter, which provides a reading in numbers . Digital meters are easier to read and provide a more accurate reading than analog meters.
However, analog meters provide a better graphic display of rapid changes in current or voltage.

## TYPES OF METERS

• An ammeter is used to measure current in a circuit. An ammeter can be considered a flow meter. It measures the number of electrons flowing past a given point in a circuit. The electrons must flow through the ammeter to obtain a reading , and this is accomplished by opening the circuit and inserting the ammeter.
• A voltmeter is used to measure the voltage (difference of potential) between two points in a circuit. A voltmeter can be considered a pressure gauge, used to measure the electrical pressure in a circuit .
• Resistance is measured with an ohmmeter. To measure resistance, a voltage is placed across the device to be measured, inducing a current flow through the device. When there is little resistance, a large current flows and the ohmmeter registers a low resistance. When there is great resistance, a small current flows and the ohmmeter registers a high resistance.

## MULTIMETERS

When working on a piece of equipment, many different measurements must be taken. To eliminate the need for several meters, the voltmeter, ammeter, and ohmmeter can be combined into a single instrument called a multimeter. An analog multimeter is referred to as a volt-ohm-milliammeter (VOM). A digital multimeter is also referred to as a DMM.