Urrea UD88 User's Manual And Warranty Information page 66

E N G L I S H
Connect:
- Jumper wires between the fuel injector and the
harness connector.
- Black test probe to a good Ground at the fuel injector
or the negative (-) vehicle battery post.
- Red test probe to the fuel injector solenoid driver
input on the jumper cable.
Start the engine. A PULSE-WIDTH in milliseconds
should be read If reading is too high or unstable,
adjust the trigger level pressing the ± TRIG button
repeatedly.
Frequency (Automotive Hz) Measurements
Frequency (Hz) is the number of times a voltage
pattern repeats positive compared to negative. "On"
compared to "Off", during 1 second of time.
There are many sensors and signals on a vehicle that
have a frequency that can be measured.
Wheel Speed sensors, Vehicle Speed sensors, Fuel
injector control signals, Cam and Crank outputs and
engine reference signals are good examples.
This example measures the frequency output of a
digital Mass Air Flow sensor. Depending on the type of
MAF sensor, the output can be from several hundred
to ten thousand Hz.
NOTE: Although similar appearance, MAF sensors made
by different manufacturers function differently, have
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different frequency range's square waves and are not
interchangeable. Voltage level of square waves should be
consistent. Frequency should change smoothly with engine
load and speed.
To measure frequency (Hz):
- Select the RPM IG range with the rotary switch.
- Press the % DUTY button until Hz appears on the
right side of the display.
Insert:
- Black lead into COM jack.
- Red lead into VΩRPM CAP jack.
Connect:
- Jumper wires between the MAF sensor and the
harness connector.
- Black test probe to the Ground jumper wire.
- Red test probe to the signal output jumper wire.
Start the engine. At idle, note the frequency displayed
on the Meter. Move the throttle and note the change
in the displayed frequency. If reading is unstable,
adjust the trigger level pressing the ± TRIG button
repeatedly.
DWELL Measurements
DWELL is the number of degrees of distributor
rotation where the points remain closed. DWELL
can be measured for 1, 2, 3, 4, 5, 6, 8, 10, 12 cylinder
engines using the Meter so you need to determine
how many cylinders are in the engine to measure
DWELL.
In the DWELL mode, the Meter defaults to 4 cylinders
and the negative (-) slope so DWL° CYL, TRIG and –
appear on the display.
If you want to select another cylinders number, press
the CYL (RANGE) button repeatedly to select the
required number of cylinders. This exercise shows how
to measure DWELL.
To measure DWELL:
- Select the RPM IG range with the rotary switch.
- Press the DWL button until DWL°, CYL, TRIG and
– appear on the display.