About Multimeter

A multimeter or a multitester, also known as a volt/ohm meter or VOM, is an electronic measuring instrument that combines several functions in one unit. A multimeter designed to measure electrical quantities. A typical multimeter can measure alternating- and direct-current potential differences (voltages), current, and resistance, with several full-scale ranges provided for each quantity. There are two categories of multimeters, analog multimeters and digital multimeters (often abbreviated DMM or DVOM). Many kinds of special-purpose multimeters are manufactured to meet the needs of such specialists as telephone engineers and automobile mechanics testing ignition circuits.


History

Multimeters were invented in the early 1920s as radio receivers and other vacuum tube electronic devices became more common. As modern systems become more complicated, the multimeter is becoming more complex or may be supplemented by more specialized equipment in a technician’s toolkit. For example, where a general-purpose multimeter might only test for short-circuits, conductor resistance and some coarse measure of insulation quality, a modern technician may use a hand-held analyzer to test several parameters in order to validate the performance of a network cable.


Analog Multimeter

Analog Multimeter

Analog multimeters are instruments that are used to measure electrical quantities such as voltage, current, resistance, frequency and signal power. Basic functionality includes measurement of potential in volts, resistance in ohms, and current in amps. Analog multimeters are used to find electronic and electrical problems. Advanced units come with more features such as capacitor, diode and IC testing modes. Analog multimeters use a needle along a scale. Switched range analog multimeters are very cheap but are difficult for beginners to read accurately, especially on resistance scales.

Advantages using analog multimeter :
  1. Continuous movement of the pointer permits monitoring of how the value changes
  2. Analog multimeters can be used to find electronic and electrical short circuit problems.
  3. It is easier to follow a slowly changing voltage by watching the needle on an analog display

Disadvantages using analog multimeter :
  1. When resistance is to be measured, an 0Ω adjustment is necessary each time the range is changed
  2. There is always a risk of oscillations due to instability.
  3. The value may differ widely from the actual value when the range is changed


Digital Multimeter

A digital multimeter or DMM is one of the most widely used pieces of test equipment today. DMMs are available very cheaply and these digital multimeters can provide very high degrees of accuracy when measuring the parameters within an electronics or electrical circuit. As a result, DMMs are one of the most indispensable pieces of test equipment available today.

Digital multimeters or DMMs can measure a variety of different parameters within an electrical circuit. The basic DMMs can measure amps, volts and ohms, as the older analogue meters did, but with the ease of incorporating further functionality into an integrated circuit, many digital multimeters are able to make a number of other measurements as well. Many of them include functions such as frequency, continuity (with a buzzer to facilitate easy measurements when looking at the circuit board), capacitance, temperature and often a number of other measurements as well.

Advantages using digital multimeter
  1. Auto-polarity for direct-current readings, shows if the applied voltage is positive (agrees with meter lead labels) or negative (opposite polarity to meter leads).
  2. Sample and hold, which will latch the most recent reading for examination after the instrument is removed from the circuit under test.
  3. A graphic representation of the quantity under test, as a bar graph. This makes go/no-go testing easy, and also allows spotting of fast-moving trends
Disadvantages using digital multimeter
  1. May require memory.
  2. Repeated inputs are possible.


Digital multimeter in action



References
  1. Wikipedia : Multimeter
  2. Wikianswer : What are advantage and disadvantage of analog and digital signal?
  3. Multimeter: Definition from Answers.com
  4. Multimeter History | Digital Multimeter Blog
  5. Multimeter - University of Innsbruck
  6. Analog Multimeters Information on GlobalSpec

P.S : The article above is some of my group's assignment that required by my lecturer.
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