User Manual

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UT108/109 OPERATING MANUAL
UT108/109 OPERATING MANUAL
66
5. RPM Testing (see gure 20)
(1) Set the rotary switch to RPMx10 and select the number of cylinders in the automobile
to be tested.
(2) Insert the red test lead into the terminal and the black one into the COM terminal.
(3) Connect the black test lead probe to the ground (i.e. ground strap connection) of the
automobile and the red one to the appropriate testing test terminal of the computer
of the automobile if the automobile is in a DIS type (Refer to the servicing handbooks
of various kinds of automotive manuals for the detailed position); or the negative
pole of the ignition coil if the automobile is equipped with a distributor board (Refer to
the servicing handbooks of various kinds of automotive manuals for the detailed
position).
(4) The normal starting rotation speed of an engine is about 50 RPM to 275 RPM. Refer
the detailed position to the servicing handbooks of various kinds of automotive
manuals because this value relates to the then temperature, engine size, battery size,
etc..
Warning:
The displayed value of the meter becomes the actual tach reading only after it is
multiplied by 10.