ACTIVITY – A2
AIM:
To measure resistance, voltage (AC/DC), current (AC)
and check continuity of a given circuit using
multimeter.
APPARATUS REQURIED:
Multimeter
Carbon resistors
Cartridge fuse
Step-down resistor
Battery cell
One-way key
THEORY:
The multimeter is an instrument used ofr measuring
the current, voltage (AC/DC) and resistance
(high/low). It is also known as AVO meter where A
stands for current in amperes, V stands for voltage in
volt and O stands for resistance in ohm.
Carbon resistors are small in size and made of
carbon. Their values are given using a colour code. To
remember the colour sequence in the increasing
order of the number assigned to the colour BBROY
GB VGW named after BB Roy of Great Britain is Very
Good Worker.
DIAGRAM:
Procedure:
a. To measure resistance
1. Check and mark the given carbon resistor as
X1, X2 and X3.
2. Record the coloured bands marked on them
in proper order and find their resistance with
the help colour code table.
3. Set the multimeter to proper resistance range
according to the value of resistance to be
measured.
4. Touch the two leads of multimeter directly
and adjust the pointer to zero reading by
adjuster knob.
5. Touch the two leads of the multimeter to the
terminals of the given resistance. Record the
reading of the resistance from the meter.
6. Repeat the above steps with other resistance
X2 and X3.
B. To Measure AC Voltage
1. Set the multimeter knob to AC voltage range
from 100 V.
2. Connect the leads of the multimeter to the
terminals of the secondary coil of the given
step-down transformer.
3. Switch on the transformer circuit and record
the AC voltage output of the transformer.
4. Repeat the above steps with other values of
tapping of battery eliminator.
C. To Measure DC Voltage
1. Set multimeter knob to DC voltage range 0 to
10 V.
2. Touch the(two) appropriate leads to the
positive terminal and the negative terminal of
the cell. Record the voltage.
D. To Measure AC/DC Current
Proceed as for AC/DC voltage but taking care that
the leads of the multimeter are in series with
appropriate circuit.
E. Continuity Check
1. Set the multimeter to measure resistance.
2. Connect the two terminals (leads) of the
multimeter directly. Adjust the reading to zero.
3. Touch the ends of the cartridge fuse with the
leads of the multimeter. If the value of
resistance drops to very low, it indicates
continuity of the fuse. If the resistance is infinite
i.e. the multimeter is not affected by the
cartridge fuse, it indicates discontinuity.
OBSERVATIONS:
G
A
RESULT:
1. Within the experimental error limits, the value
of carbon resistor calculated by colour coding
and measured with the help of multimeter is
same.
2. Voltage (AC/DC) measured by the multimeter is
same as the value of voltage marked on
(AC/DC) source.
PRECAUTION:
1. Read the instructions before using multimeter
to avoid it getting damaged.
2. Pass the alternating current for the minimum
possible time.
3. In measuring DC voltage/current, polarity
probe leads should be connected to the
proper polarity in the circuit.
SOURCES OF ERROR:
1. When we measure resistance using analog
multimeter , zero adjustment may not be
accurate.
2. Selection of function switch may be
inappropriate.
3. The scale/ range used is reading of voltage/
current may not be proper.
