UNI-T UT108, Operating Manual

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UT108/109 OPERATING MANUAL
44
K
. Engine Tach (Rotation Speed) Testing “RPMx10”
(see figure 14)
The RPM means the rotating frequency of the main shaft of the engine per minute.
1. Set the rotary switch to RPM X10 DWELL . Press RANGE button to select the number
of cylinders and press BLUE button to select RPM X10 measurement mode.
2. Insert the red test lead into the V terminal and the black one into the COM terminal.
Select an appropriate number of cylinders. Connect the ends to be tested as illustrated.
● If a DIS ignition system without any distributor board is used in the automobile,
connect the red test lead probe to the TACH (tachometer) signal line (which is
connected to the computer DIS module of the automotive engine). Refer to the
automotive servicing manual for the specific position.
● If an ignition system with a distributor board is used in the automobile, connect the red
test lead probe to the primary negative end of the ignition coil. (Refer to the
automotive servicing manual for the specific position.)
3. Connect the black test lead probe to the good ground terminal of the automobile.
4. Upon the start of the engine or during its operation, test the rotation speed of the engine
and read the displayed value from the display. The actual rotation speed of the
automobile to be tested should be equal to the displayed value multiplied by 10. For
example, the actual rotation speed of the engine of the automobile should be 2000