AUT500-EU-EN v1.0 5/13
12
ms-PULSE (Pulse Width in milliseconds)
Pulse width is the length of time an actuator is energized. For example, fuel injectors are activated by
an electronic pulse from the Engine Control Module (ECM). The pulse generates a magnetic field that
pulls the injector’s nozzle valve open. The pulse ends and the injector nozzle is closed. This ‘open to
close’ time is the pulse width and it is measured in milliseconds (ms). The most common automotive
application for measuring pulse width is fuel injection. The pulse width of the fuel mixture control
solenoid and the idle air control motor can be measured. The next measurement section describes
how to measure pulse width on port fuel injectors.
PULSE WIDTH MEASUREMENT EXAMPLE
1. Set the rotary function switch to the
ms-PULSE
position.
2. Insert the black lead banana plug into the negative
COM
jack and the red test lead banana plug
into the positive
ms
jack.
3. Press the RANGE key momentarily to select
TRIG -
in the display (the applied time for most fuel
injectors is displayed on the negative slope).
4. Add a jumper cable between the fuel injector and the harness connector.
5. Connect the black test lead to a good ground at the fuel injector or the negative vehicle battery
post.
6. Connect the red test lead to the fuel injector solenoid driver input on the jumper cable (from step 4).
7. Start the engine.
8. Read the pulse size in milliseconds on the display, Note: Initially the meter will read OL (over
range) and then readings will descend and stabilize to the actual pulse width. If OL remains on the
meter display, re-check the connections and test setup.
DWELL MEASUREMENTS
1. Set the rotary function switch to the
DWELL
position.
2. Insert the black lead banana plug into the negative
COM
jack and the red test lead banana plug
into the positive
DWELL
jack.
3. Touch the test leads to the breaker points’ wire (red test lead) and to a good ground (black test
lead).
4. Select the number of engine cylinders (4, 5, 6, or 8) using the RANGE button.
5. Read dwell angle in degrees on the LCD.
RPM MEASUREMENTS
1. Set the rotary function switch to the
RPM
or the
x10 RPM
position. Use the x10 position for
readings 1000 to 12000 RPM.
2. Connect the supplied magnetic clamp pickup to the meter by inserting the black lead banana plug
into the negative
COM
jack and the red test lead banana plug into the positive
RPM
jack.
3. Clamp the magnetic pickup around the spark plug wire to sense secondary ignition impulses.
4. Read the RPM on the display. When using the x10 mode, multiply the reading by a factor of 10.
RPM Measurement notes:
If no signal is detected, unclamp the pickup from the spark plug wire and re-clamp around the
spark plug wire in the opposite direction.
Position the pickup so it is 6 inches from the spark plug. If no signal is detected or if an erratic
signal is detected try another spark plug wire.
Position the magnetic pickup as far from the distributor and exhaust manifold as possible.
