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ELEC 103
LABORATORY EXERCISE 1
USE OF THE MULTIMETER
PURPOSE OF EXPERIMENT
The purpose of this experiment is to determine the resistance of two circuit components, light bulb #1
and light bulb #2. In this experiment, you will determine the resistance of the light bulb's by measuring
the current flowing through each bulb and the voltage drop across each bulb. Then Ohm's Law will be
used to calculate the resistance of each bulb by dividing the voltage measured across the light bulb by
the current measured flowing through the light bulb.
EQUIPMENT LIST
1  DC Power Supply
2  6V Light Bulb's
1  Simpson Model 260 VOM
PROCEDURE  PART 1
1.
Carefully examine the Simpson Model 260 multimeter
and note the location and configuration of the
following controls and scales:
RANGE/FUNCTION SWITCH is located in the center of
the control panel. It has 12 positions including five
positions for voltage. They are oriented to the left.
Four positions for current are located across the top
and upper right. And three positions for resistance
located to the right.
STATUS/POLARITY SWITCH is located on the left side
of the control panel. This switch usually has an off or
transport position, a +DC position, a DC position,
and an AC position.
ZERO OHMS ADJUST KNOB is located on the right side
of the control panel. This knob is used to adjust the
meter pointer to zero ohms on the resistance ranges
when the meter leads are connected together.
DC SCALE is the second scale down from the top under the
glassed portion of the multimeter. It is sometimes located directly under the parallax mirror.
This scale is used for all DC voltage and current ranges. The scale is divided into 50 divisions
and is similar to the scale used in the figures during your Unit One learning experiences. When
using the 2.5 volt range switch position and when using the 500 volt range/function switch
position, you must mentally move the decimal point to the appropriate position. On all other
range switch positions the numbers on the scale are appropriate.
COMMON () AND PLUS (+) RECEPTACLES are located in the lower left corner of the control
panel. Always make certain the black lead is connected to the minus or negative receptacle and
the red lead is connected to the plus or positive receptacle.
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ELEC 103
LABORATORY EXERCISE 1
USE OF THE MULTIMETER
PROCEDURE  PART 2
NOTE: It is not always possible to determine the
approximate value of the current flowing in a circuit before
you measure it with the milliammeter. Therefore, when the
milliammeter is connected in series with the element you
should start with the range switch adjusted to the highest
current measuring range. After power has been applied to
the circuit, adjust the range switch to lower current ranges
until you obtain an appropriate current measurement. If the
meter pointer moves to the left, reverse the meter leads and
continue with the experiment.
1. Connect the circuit as shown in Figure 11. Be
certain to connect the milliammeter to the circuit so it
is connected in series with the circuit. Additionally,
connect the meter to the circuit observing correct
polarity. The negative lead of the milliammeter is
connected toward the negative or ground side of the
power source, and the positive lead is connected
toward the positive side of the power source. Use the
highest current range possible.
2. Close the switch. (Turn the switch on.) You should see no current flow indicated by the meter
pointer since you are on a very high
current range. Adjust the range/function
switch to the next lower current
measuring range position. Continue
doing this until the meter pointer moves
up scale when you have adjusted the
range/function switch to a lower range.
Your reading on the meter will tell you
if it is safe to go to the next lower scale.
For example, if the meter pointer shows
a reading of 15 milliamperes when it is
Figure 11
on the 100 milliampere range, then it
would NOT be safe to go to the 10
milliampere range.
CONCLUSION
The resistance of a component can be determined by calculation when the voltage across the
component and the current through the component has been measured.
NOTE: The resistance of the bulb is different when the bulb is HOT than when it is cold. The
resistance of the bulb cannot be measured directly when it is hot and has current flowing
through it. However, the resistance of the bulb's filament can be determined indirectly using
the voltage and current measurements, and Ohm's Law as was done in this experiment.
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ELEC 103
LABORATORY EXERCISE 1
USE OF THE MULTIMETER
DATA TABLES
4.
5.
6.
Record
the current
you
measured in step 3 in the box to
the right.
It = ____________ mA
Measure the voltage across light
bulb #1 and record it as V1. The
correct polarity must be
observed when connecting the
voltmeter to the circuit.
V1 = ___________ V
Measure the voltage across light
bulb #2 and record it as V2 The
correct polarity must be
observed when connecting the
voltmeter to the circuit.
V2 = ___________ V
7. Calculations using Ohms Law:
R1 =
Volts
Amps
R2 =
Volts
Amps =
8. Calculations using Ohms Law:
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=
R1 = ____________ 
R2 = ____________ 