Principle: The current temperature controllers are all liquid expansion structures. The liquid has the characteristics of thermal expansion and contraction, the temperature controller seals the special liquid in the sealing cavity composed of the probe tube and the capillary tube, and the probe tube is inserted into the temperature to be measured, and when the temperature rises, the liquid in the probe tube expands and along The capillary moves to the end, and the expanded liquid pushes the bellows to push the contacts, causing the circuit to break and stop heating. Adjusting the thermostat knob, that is adjusting the amount of displacement that breaks the contact, and this amount of displacement is proportional to the sensed temperature. When the temperature drops, the expanded liquid will gradually shrink the volume, the contact will return to the conduction state, and the heating element will start to heat again. This is the principle that the temperature controller controls the water temperature

Detection method:

Measure whether the thermostat is on or off:Remove the connecting line, the multimeter hits the resistance × 10 files, after zero adjustment, the two terminals should be turned on by the meter, Otherwise the thermostat is judged to be damaged, the thermostat needs to be replaced(the adjustable temperature controller should turn the knob to the highest temperature position) . Use the test leads to measure the two terminals and the metal casing should be non-conductive,Otherwise the thermostat is judged to be damaged, the thermostat needs to be replaced.

2.Over-temperature protector (thermal breaker/thermal cut)

Principle:The over-temperature protector utilizes the principle of thermal deformation of the metal sheet, when the metal sheet senses the deformation temperature, the bimetal sheet produces the overall deformation, pushes the push rod movement to make the contact point disconnect, thus cutting off the heating power supply, thus achieving the purpose of ultra-high temperature protection.

Detection method:

Whether the over temperature protector is on or off:Remove the connection wire,and after the multimeter is set to zero in resistance 10, measure the two terminals with the meter pen. Normally, it is on, Otherwise, the over-temperature protector is damaged, and the over-temperature protector needs to be replaced. Use the test leads to measure the terminal and the metal casing should be non-conducting,otherwise the over-temperature protector is damaged and the over-temperature protector needs to be replaced.

3. Heating element

Principle: Electric energy → thermal energy conversion device, the heating element uses water to heat the function.

Detection method: ①The multimeter is in the resistance × 10 steps, Measure the resistance between the two terminals, the electric tube is in normal condition,within normal error range (307 Ω ~ 358 Ω to 1500 W for example), When value being infinity, the heating element is disconnected, and the heating element needs to be replaced, When the temperature is too small, the heating element is aging, the power is reduced, and the heating element needs to be replaced.②The multimeter is playing in the resistance × 10 files (or 2MΩ files), the red pen is connected to the terminal, and the black pen is connected to the mounting plate. The measured resistance should be greater than 2MΩ. Otherwise, the heating element is judged to be damaged by insulation, and the heating element 

needs to be replaced to prevent leakage.