Measuring Resistance; Measuring Dc Current - Actron AutoTroubleShooter Operating Instructions Manual

Measuring Resistance

Resistance is measured in electrical
units called ohms (Ω). The digital multi-
meter can measure resistance from 0.
1Ω to 20MΩ or (20,000,000 ohms). Infi-
nite resistance is shown with a "1" on the
left side of display (See Setting the
Range on page 6). You can use this
multimeter to do any resistance mea-
surement called out in the vehicle ser-
vice manual. Testing ignition coils, spark
plug wires, and some engine sensors
are common uses for the OHMS (Ω)
function.
Fig. 9
600
600
To measure Resistance (see Fig. 9):
1. Turn circuit power OFF.
To get an accurate resistance mea-
surement and avoid possible damage
to the digital multimeter and electrical
circuit under test, turn off all electrical
power in the circuit where the resis-
tance measurement is being taken.
2. Insert BLACK test lead into COM
test lead jack.
3. I n s e r t R E D t e s t l e a d i n t o
4. Turn multimeter rotary switch to
200Ω range.
Touch RED and BLACK multimeter
leads together and view reading on
display.
Display should read typically 0.2Ω to
1.5Ω.
If display reading was greater than
1.5Ω, check both ends of test leads
for bad connections. If bad connec-
tions are found, replace test leads.
5. Connect RED and BLACK test
leads across component where
you want to measure resistance.
Unknown
Resistance
Red Black
test lead jack.
W h e n m a k i n g
measurements, polarity is not
important. The test leads just have
t o b e c o n n e c t e d a c r o s s t h e
component.
6. Turn multimeter rotary switch to
desired OHM range.
If the approximate resistance is un-
known, start at the largest OHM
range and decrease to the appropri-
ate range as required. (See Setting
the Range on page 6)
7. View reading on display - Note
range setting for correct units.
NOTE: 2K Ω = 2 ,000Ω;
2MΩ = 2, 000,000Ω
If you want to make precise resis-
tance measurements, then subtract
the test lead resistance found in
Step 4 above from the display
reading in Step 7. It is a good idea to
do this for resistance measurements
less than 10Ω.

Measuring DC Current

This multimeter can be used to measure
DC current in the range from 0 to 10A. If
the current you are measuring exceeds
10A, the internal fuse will blow (see Fuse
Replacement on page 7). Unlike voltage
and resistance measurements where the
multimeter is connected across the com-
ponent you are testing, current measure-
ments must be made with the multimeter
in series with the component. Isolating
current drains and short circuits are some
DC Current applications.
To measure DC Current (see Figs. 10 &
11):
1. Insert BLACK test lead into COM
test lead jack.
2. Insert RED test lead into "10A"
test lead jack or "mA" test lead
jack.
3. Disconnect or electrically open
circuit where you want to mea-
sure current.
This is done by:
• Disconnecting wiring harness.
• Disconnecting wire from screw-on
10
r e s i s t a n c e