Multimeters (DVOM)

Introduction

Multimeters or Digital Volt Ohm Meters (DVOM)'s as they are sometimes known are used extensively by technicians in the automotive industry as a basic electrical test tool. In fact, in the hands of a qualified operator the DVOM can be used to diagnose very complex problems in vehicle electrical systems, however the requirement of this practice is much reduced with the advent of "on-board" diagnostics and the use of scan tools.

There are several types available with an equally diverse range of prices to suit. The more substantial types have more functions and are generally more reliable. In some locations many meters are known more commonly by their "brand" name.

Description

The DVOM is an electronic measuring instrument that combines several functions in one unit. The most basic instruments include an ammeter, voltmeter, and ohmmeter.

Normally the meter has a central rotating selection switch which is used to select the electrical test function that the meter is going to be used for, and a set of input points that are used to connect the meter to the item/circuit being tested by test leads. Most meters also have a safety fuse fitted (of about 10 amps maximum) into them for operational safety and to prevent damage to the meter should it be connected to excessive electrical loads.

Features available in some units

Some of the features that these meters have are:

1. A continuity tester that beeps when a circuit conducts.
2. Digital output (as a number, rather than a scale reading) of the quantity under test.
3. An amplifier to sense small voltages, currents and high resistance's.
4. Measurements of inductance and capacitance. This is helpful to test components, and therefore much used by technicians that must build and repair equipment.
5. Tests of diodes and transistors. This is popular with technicians who have to fix broken equipment.
6. Scales and sockets for temperature measurement with standard thermocouples.
7. An intermediate-frequency oscillator, a detector and an audio amplifier with a speaker, to diagnose and tune radio circuits. This used to be standard on some Russian models. It is an inexpensive compact substitute for an oscilloscope. It permits one to hear a signal, rather than see it.
8. A slow oscilloscope. This is appearing in some high-end computer-controlled multimeters.
9. A telephone test set.
10. Automotive circuit tester.
11. Record high and low voltage snapshots

Source: CDX Global & Wikipedia - en.wikipedia.org