Multimeter

Hi friends! This time I am introducing one of the measurement devices i.e. Multimeter. This is the device which is used by people irrespective of age. Basically a Multimeter can be defined as an electronic measuring instrument which includes the ability to measure the voltage, current and resistance. Multimeter can also be called as VOM (Volt-Ohm-Meter). A multimeter can be used as the basic fault finding device for house hold electrical faults.

AVO meter

Multimeters were invented in the early 1920s by a British Post Office Engineer, Donald Macadie, Macadie invented an instrument which could measure amperes, volts, ohms, and hence it was named as "Avometer". The meter comprised of a moving coil meter, voltage and precision resistors, and switches and sockets to select the range. The first AVO was put on scale in 1923, and although it was initially a DC. Many of its features remained almost unaltered through to the last model.

There are two types of multimeter. They are:-

1. Analog multimeter (AMM).
2. Digital multimeter (DMM).

1. Analog multimeter:-

 Analog mutimeters 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. These are used to find electronic and electrical problems. It contains advanced features like capacitor, diode testing and IC testing modes.. Analog multimeters can sometimes be difficult to read because they display data as needle moving along a scale this is the major disadvantage of it because when the operator reads the output then the reading will not be as accurate as of the reading in digital 

2. Digital multimeter (DMM):-

The digital multimeter is a versatile and most common digital measuring instrument that can be used for assembling, testing, and servicing laboratories. It displays the measurement of ac or dc voltages, dc or ac currents and resistance of discrete numerals. It is a handy and more accurate compared to analog meter.

These are instruments that are used to measure electrical quantities such as voltage, current, resistance, capacitance and time period. DMMs are generally bench top or hand held. Bench top models can also be portable by use of handles and wheels. Hand held multimeters are designed to be used while holding i.e. can be operated by with one hand. DMMs display information on a digital screen. Commonly they have between 3 and 6 digits, but some units come with larger screens that can display 7 or ore digits.

Advantages of DMM:-

DMM offer many advantages over analog multimeters, such as speed in reading, increased accuracy, better resolution, and capability of automated operation. DMM are available to read current, resistance, and AC or DC voltages directly without any parallax errors.

SL no	Parameters	Analog multimeter	Digital multimeter
1	Power supply	Not required	Required
2	Visual indication of changes in reading	Better	Not better
3	Effect of electric noise	Less	More
4	Isolation problems	Less	More
5	Accuracy	Less	High
6	Interface of the output with external equipment	Not possible	Possible
7	Construction	Simple	Complicated
8	Cost	Less	More
9	Size	Bigger	Smaller
10	Nature of output	Ambiguous many times	Unambiguous  reading

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