UNI-T UT108, Operating Manual

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UT108/109 OPERATING MANUAL
UT108/109 OPERATING MANUAL
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1. Oxygen Sensor
The oxygen sensor is used to test the oxygen content in the exhaust, giving rise to an
appropriate voltage or resistance. A low voltage (high resistance) means too high oxygen
content in the exhaust, while a high voltage (low resistance) means too low oxygen
content. The computer regulates the ratio between the air and the fuel according to the
high or low voltage. There are normally two types of oxygen sensors: the zirconia and
titania sensors. (Refer to the different external properties of the two types for the details.)
Testing Procedure:
(1) Move the oxygen sensor out of the automobile.
(2) Set the rotary switch to
Ω . Insert the red test lead into the Ω terminal and the black one
into the COM terminal.
(3) Connect the black test lead probe of the meter to the ground terminal (i.e. cold end) of
the sensor.
Warning:
If the sensor has a 1- or 3-lead outlet, the ground terminal is its shell.
If the sensor has a 2- or 4-lead outlet, the ground terminal is its special wiring.
(4) Connect the red test lead probe of the meter to the signal terminal (i.e. hot end) of the
sensor.