Radio Shack 22-812A, Manual, Page: 12 / 24

1
MASTER BKGRD 6-26-07
Taking Measurements
MASTER BKGRD 6-26-07
Measuring DC/AC Voltage
WARNING : Do �OT try to measure a DC �oltage abo�e 1000 �olts or an AC
voltage above 750 volts RMS, and never clamp a test lead to a hot wire (usually
red, black, or blue in AC wiring circuits). if one lead is clamped to a hot wire and
you touch the meter’s other probe, you could recei�e an electric shock.
1. To measure DC �oltage, set the function dial to
ºC/ºF / V and press SELECT
to select DC �oltage measurement.
To measure AC �oltage, set the function dial to dBm / V and press SELECT
to select dBm or �olts unit.
2. if the meter is set to automatic range control, the meter automatically mo�es
to the range that gi�es the best reading.
To set manual range control, press RANGE then change the range (if
necessary) by pressing RANGE .
3. Touch the test leads to the circuit you want to test.
Notes :
• when the meter is set to the 400mV range,
OF
continues to appear e�en after you
remo�e an o�er-range input signal. This is not a malfunction.Touch the test leads
together or connect them to a circuit, then
OF
disappears.
• 0 d�m is e�ual to the consumption power on a �00-ohm resistor with 0.775V voltage 0 d�m is e�ual to the consumption power on a �00-ohm resistor with 0.775V voltage
drop.
You can also follow steps 1-3 abo�e to measure AC �oltage superimposed on a
DC �oltage source bias while ignoring the DC �oltage, but ne�er try to measure
ne�er try to measure try to measure
an AC �oltage that is riding on a DC source bias where the peak AC �oltage
e�ceeds 1000 V with respect to earth ground.
Measuring DC/AC Current
To measure DC/AC current, you must break the circuit and connect the test leads
to two circuit connection points. The connection must be in series with the circuit
under test.
WARNING:
• �e�er connect the test leads across a �oltage source. Doing so can damage
the meter or the circuit under test. The ma�imum input limit for AC/DC current
measurement is 10A.
• if you do not know the amount of current in the circuit you are measuring, always
connect the red test lead to +10A MAX.