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OPERATING AND TESTING THE MULTIMETER
CAUTION:
When measuring an unknown voltage or current, always start with the range switch set to the
highest scale. Then, if necessary, move the range switch down until the meter reads in the middle or right half
of the dial.
Checking your multimeter for proper operation is fairly easy. Of prime importance is knowing which scale is read
for each setting of the range switch. DC voltage is read on the dial immediately below the meter mirror. This
dial is marked with three scales with full scale readings of 10, 50 and 250. The 0-10 scale is used for DC voltage
ranges of .1, 10 and 1000VDC. The 0-50 scale is used for DC voltage ranges of .5 and 50VDC and the 0-250
scale is used for DC voltage ranges of 2.5 and 250VDC. The readings taken on these scales must be multiplied
by the proper scale factor. For example, when the range switch is in 2.5VDC, a full scale reading on the 0-250
scale is actually 2.5 volts. You should therefore multiply your reading by .01 (move the decimal point 2 places
to the left). DCmA are read using the same three scales as DC volts.
AC volts are read on the red dial marked ACV using the same 0-10, 0-50 and 0-250 scales as used for DC volts.
AC volts may also be read in decibels using the dB scale. The reference voltage (0dB) for the dB scale is .775
volts. This voltage across 600 ohms dissipates 1mW of power. When dBs are read with the range switch at
10ACV, the dB scale is read directly to 22dB. With the range switch at 50ACV add 14dB. With the range switch
at 250ACV add 28dB and at 1000ACV add 40dB. The maximum dB readable is 22 + 40 = 62 (dB) measured
on the 1000ACV scale.
Ohms are read on the top scale. Multiply the reading by the appropriate factor 1, 10, 1k or 10k as indicated by
the range switch.
If you are new to reading analog meter scales, assemble and try the Dial Scale Reading Exercise
included with this kit.
Before starting tests, set the meter needle to zero . The zero adjust screw is located on the meter face next to
the base of the needle. With no test leads connected, slowly turn this screw until the needle points to zero on
the 0-10 scale immediately below the meter mirror. We will now test each meter function. If the meter should
fail to perform as indicated, refer to the troubleshooting section for assistance.
DC Voltage Test
1) Plug the red test lead into the positive (+) socket, and the black lead into the –COM socket.
2) Set the range switch to 2.5VDC.
3) Connect the red lead to the positive side of a 1.5V battery (you may remove and use one of the 1.5V
batteries from the meter). Connect the black lead to the negative side of the battery. The meter should read
about 150 on the 0-250 scale. Move the decimal point 2 places to the left to obtain 1.5VDC.
4) Set the range switch to 10VDC. The meter should read 1.5 on the 0-10 volt scale.
5) Set the range switch to 50VDC. The meter should move about 1 1/2 small divisions on the 0-50 volt scale.
Ohms Test
CAUTION:
When measuring ohms, be sure that there is no voltage across the circuit being tested.
1) Plug the red test lead into the positive (+) socket, and the black lead into the –COM socket.
2) If you removed the 1.5 volt battery from the multimeter for the DC voltage test, replace it now.
3) Set the range selector switch to X1.
4) Short the test leads together and adjust the 0
Ω
ADJ pot for a zero reading on the ohms (top) scale.
5) Connect the test leads to a known resistor between 1 and 100 ohms and observe the meter reading. Multiply
by the scale factor to obtain the resistance.
6) Set the range switch to X10 and repeat steps 4 and 5 using a 10 to 1k ohm resistor.
7) Set the range switch to X100 and repeat steps 4 and 5 using a 1k to 10k ohm resistor.
8) Set the range switch to X1k and repeat steps 4 and 5 using a 10k to 100k ohm resistor.
9) Set the range switch to X10k and repeat steps 4 and 5 using a 100k to 1M ohm resistor.
