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    In the use of household appliances, people's use of air conditioners is indispensable. When we use air conditioners to adjust the temperature, have you ever thought about why air conditioners can automatically turn on, turn off, and adjust the temperature and wind speed? Let's talk about the well-known temperature sensors!

    Air conditioner temperature control mainly uses temperature sensors to detect room temperature changes for cooling and heating, control the power on and off of the compressor, and thus control the cooling or heating temperature of the air conditioner. The temperature control of the air conditioner mainly refers to the detection of the ambient temperature by the temperature sensor under the unified command of the CPU, and compares it with the manually set temperature. When the corresponding temperature is reached, the CPU controls the power on or off of the compressor. The temperature control range of the air conditioner is generally between 16℃ and 30℃. When cooling, the minimum set temperature will not be lower than 16℃, and when heating, the maximum set temperature will not be higher than 30℃.

    The air conditioner temperature sensor is connected in series with a resistor, and generally uses a 5V (+3.3V used by some air conditioners) voltage for voltage division, and the divided voltage is sent to the CPU. Since the air conditioner temperature sensor uses a negative temperature coefficient thermistor, that is, its resistance decreases when the temperature rises, and its resistance increases when the temperature decreases. Therefore, the input voltage rule of the CPU is: when the temperature rises, the input voltage of the CPU increases, and when the temperature decreases, the input voltage of the CPU decreases accordingly. This changing voltage enters the CPU for internal analysis and processing to determine the current pipe temperature or room temperature, and controls the operating status of the air conditioner through internal programs and manual program settings.

    Since the sampling voltage sent to the CPU will change in a large range with the temperature change, the manufacturer generally takes 25℃ as the standard when designing, and designs the sampling voltage to half of the power supply voltage, so as to leave sufficient room for the voltage change caused by temperature change. If the sampling voltage is designed too high or too low, it will not reflect the current temperature change normally. This is the working principle of the air conditioner temperature sensor.

    The commonly used NTCs for air conditioners are indoor ambient temperature NTC, indoor coil NTC, outdoor coil NTC, etc., and variable frequency air conditioners also use external ambient temperature NTC, compressor suction, exhaust NTC, etc. In the circuit, the temperature change of NTC changes the resistance of NTC, and the voltage of CPU terminal also changes accordingly. CPU judges the temperature of air conditioner according to the change of voltage, thus determining the working status of air conditioner.

    Common faults of NTC include resistance increase, open circuit, resistance change due to moisture and mildew, short circuit, poor contact between plug and socket or leakage, etc., which cause abnormal voltage of air conditioner CPU detection terminal and thus air conditioner failure. Temperature sensor is a thermistor semiconductor device. Damage conditions include resistance increase, resistance decrease, open circuit, short circuit, mildew, rust, poor plug contact, broken wire, resistance change with temperature characteristics deterioration, signal transmission circuit damage, etc. When the temperature sensor has obvious open circuit or short circuit, CPU control is in the air conditioner protection state, and other conditions cause the air conditioner to be unable to operate normally. In actual maintenance, it is found that the most easily damaged sensors are indoor unit pipe temperature sensor, compressor exhaust temperature sensor, outdoor pipe temperature sensor, etc.

    Nanjing Shiheng Electronic Technology Co., Ltd. has a full set of technologies from chip core formula to finished product manufacturing, independent intellectual property rights, and independent control of all formulas. The company has passed five major system certifications: ISO9001 quality management system certification, TS16949 quality management system certification, ISO14001 environmental management system certification, GB/T29490 intellectual property management system certification, GB/T23001 integration of industrialization and information technology management system assessment, and has 46 patent certificates. All products are environmentally friendly in accordance with the EU RoHS directive. The main NTC thermistor products have passed CQC mark certification, German TUV certification and American UL and C-UL safety certification. The automotive-grade MF52, MF51 and MF58 have passed AEC-Q200 testing. The MF58 series products are the first domestic products to pass the 100,000-time durability test in the UL standard. They are widely used in various household appliances.