Tuesday, 7 August 2012

FAMILIARIZATION OF MULTIMETER

Multimeter is a very popular electronic measuring device. It is an essential equipment to troubleshoot an electronic circuit.
Multimeter is used to measure various electrical quantities such as voltage , current and resitance. It work in different modes namely ammeter, voltmeter and ohmmeter. The mode can be set using a selector switch provided in the multimerer.

Both AC and DC voltages and current can be measured using multivibrator. They are available in two types analog and digital. Analog multimeter have a needle moving over a caliberated scale while the digital multimeter give the digital display of the measured quantities.


A digital multumeter is made from the basic digital voltmeter. For the measurment of current , the voltage drop across a precision resistance is measured. DVM cam be converted to an ohmmeter by using an accurate current source. It measures the voltage drop across the resistance being measured.

Measurements Using analog multimeter


Zero adjustment of multimeter: Before the measurment are taken, make sure that the pointer of the meter is at zero position of the scale. If the pointer is not on the zero position , bring th pointer to.exact position by turning th screw located just below the scale window , using a small srew driver.


DC and AC voltage measurement using multimeter

1. Insert the positive and negative test leads in appropriate grooves.

2. To measure DC voltage , set the rang selector switch to the prescribed DC voltage range. Sililarly to measure AC voltage, set the range selector switch in AC voltage range.
For safety and accuracy , start with the highest range and work down by turning the range selector switch to lower ranges.


Measurement of current

1. Insret the positive lead and negative test lead of the multimeter in proper places.

2. Selector switch should be set to prescribed range before connecting the multimeter in series with the path of the current under measurement. Start taking values only after setting the selector switch in the highest range. Fir accurate measurments work down to lower ranges.

Measurement of resistance 1. Turn the range slector nob to Ω position. Then the pointer will to the exreme left of dial indicating that the resistance if infinite. Then short the connecting terminal together. The pointer will move to the right extreme where the resistance is marked zero. If the ponter does not show zero resistance, turn the 'Ω adj' knob to make the pointer read zero.

2. Connect the multimeter terminals to the resistor leads. The value of the resistance can be read from the pointer position. Turn the range selector nob to the highest range of resistance and then reduce to lower ranges to take the reading accurately.


Measurement using digital multumeter


DC and AC voltage measurement using DMM

1. Insert the positive and negative test leads in proper place.

2. Set the range selector switch to the DC V / AC V range under measurement is unknown, set the range selector switch to the highest range and work down to lower range.


DC and AC current measurement using DMM

1. Connect the positive test lead to the COM terminal and red test lead to the terminal marked 'A' for the measurement of current up to 2A. For the measurement of current in the range from 2A to 20A connect the red test lead to 20 A terminal.

2. Set the range selector switch to the DC A or AC A accordingly, and connect the test leads in series with the load under measurement.


Resistance measurement using DMM


1. Insert the positive and negative test leads in proper places.

2. Set the range selector switch to the Ω range and connect the test leads across the resistance under mesurement.
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2 comments:

  1. Good work with Nice Explanation......

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