Precautions for NTC thermal protector detection.Humidity Sensor company

　　In the communication with customers, sometimes customers ask: can the thermal protector be more sensitive, the operating temperature of the thermal protector is not accurate, the reset temperature is not accurate, our oven for temperature measurement is very accurate, and so on. This all reflects that we did not pay attention to the characteristics and laws of heat conduction when testing the temperature of the temperature switch. When conducting thermal testing, if the law of heat conduction is not followed, the testing results we get will be false or wrong.

　　Thermal conduction and electrical conduction are completely different. It takes a long time for heat conduction to reach thermal equilibrium. And whether the contact is tight, the heat transfer medium and convection will directly affect the process of heat transfer. In the temperature detection of the temperature control switch, there is still a problem that the detected object is not clear, and this temperature is not the other temperature. Let's talk about how to use the existing equipment of the general factory to correctly detect the temperature of the temperature control switch.

　　1. Testing equipment

　　Oven, thermocouple thermometer, crepe tape, LED tooling for on/off display

　　2. Detection method

　　1. Use crepe tape to tightly fix the temperature sensing head of the thermocouple thermometer on the temperature sensing surface of the temperature control switch. Be sure to use crepe tape to wrap the temperature sensing head of the thermocouple thermometer several layers to avoid exposing the temperature sensing head to the external temperature environment, in order to make the temperature sensing head of the thermometer and the temperature sensing piece inside the temperature control switch sense. The temperature is approximately the same.

　　2. Connect the two terminals of the temperature control switch to the LED tooling

　　3. Put a piece of paper on the bracket of the oven, and place the temperature control switch on the paper block (to avoid the temperature control switch and the temperature sensing head of the thermometer directly contacting the metal bracket and inner wall of the oven). Turn off the oven and let it heat up.

　　4. When the temperature in the oven reaches: when the temperature switch action temperature is -20°C, set the temperature of the oven to increase every 3 to 5°C (when the temperature in the oven reaches the set temperature, adjust the temperature of the oven again. Raise 3 to 5°C. Because most ovens in factories cannot control the speed of temperature rise, avoid the temperature rising straight up).

　　5. Until the temperature of the oven reaches the lower limit of the operating temperature of the temperature control switch, at this temperature, let the oven temperature remain constant for more than 10 minutes. Observe whether the temperature control switch operates. If the temperature control switch works, it is NG; if the temperature control switch does not work, continue the test below.

　　6. Set and increase the temperature of the oven at a rate of 1 to 2 °C, and observe whether the temperature control switch operates. Until the temperature of the oven is adjusted to the upper limit of the operating temperature of the temperature control switch. At this temperature, let the temperature of the oven remain constant for more than 10 minutes, and observe whether the temperature control switch operates. If the temperature control switch is activated, it is OK; if the temperature control switch is not activated, it is NG.

　　7. When measuring the reset temperature of the temperature control switch, do not open the oven door. Instead, turn off the power and let the oven temperature drop slowly and naturally. Observe whether the temperature control switch is reset.

　　8. The best test results above can only be approximate qualitative. The error of the thermocouple thermometer is generally 31.5 ℃. Considering the reasonable error in the detection process, the error of the detection result is reasonable at 3-4 ℃. In addition, the thermometer on the oven can only be used to monitor and set the temperature, not to read the temperature.

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