Midea 22033010000701, Service Manual

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ServiceManual_2018-V1.0
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10.3 Temperature test circuit
The characteristic that resistance value reduces as the temperature increases is deemed to have negative slope or
negative temperature coefficient (NTC), and such thermostat is called as NTC thermostat. The resistance value
changes sensitively with temperature and typically changes 7% ~ 3% per degree centigrade. Sensor used in the
refrigerator is NTC thermostat.
There is following computing formula for the sensor:
Sampling voltage / reference voltage = R1 / (RNTC + R1)
AD value / reference AD value = R1 / (RNTC + R1)
The reference voltage is 5V, RNTC is the resistance value of the sensor
The sensors work rely on the resistance value changes in accordance with the temperature, by using of the thermal
couple what has resistance and coefficient of middle temperature. This kind of thermal couple which resistance
decrease following the temperature increase is call NTC(negative temperature coefficient), the typical change of
resistance value is 7%~3% per
℃，
by using the character of voltage dividing of resistance, the specific voltage
value is sent to main PCB.
In inspection, unplug the wiring connector of sensor( picture10.4, socket 1&2 )
，
adjust the multi meter to the gear
of resistance detection, put the red probe and black probe on the corresponding pins to detect the resistance value of
sensor, then check with resistance table (10.6) to identify whether the sensor is damaged.