• 1. The Function of NTC thermistors for Thermopile in Forehead Thermometers
    In the process of prevention and control of COVID-19, medical products such as ventilator, monitor, oxygen generator, negative pressure ambulance and forehead thermometer have played an important role. The non-contact temperature measurement method of forehead temperature gun can avoid contact cross-infection, which plays a convenient and quick role in the prevention and control of epidemic situation for the general public. Forehead and ear thermometers are infrared thermometers that use thermopile to measure temperature by measuring the radiant energy emitted by objects. According to the Boltzmann's law (E=σεTⁿ), the greater the object's radiation energy, the higher the object's temperature is. When measuring the temperature, the infrared radiation signal is converted into electrical signal, which is then passed through the amplifier and signal processing circuit, and finally converted into the temperature value of the measured target according to correcting of certain algorithm and target emittance. The main components for measuring temperature is thermopile. Thermopile's infrared probe is a temperature sensor composed by thermocouples in series. The two ends of the thermocouple are composed of two different materials. When one end touches the hot end and the other end touches the cold end, a potential difference will be generated between the two materials due to "see-beck" effect, and the potential difference is related to the temperature difference between the two materials. Thermopile sensors connect a series of thermocouples to improve the sensor's detection sensitivity. In order to correctly calculate the temperature at different ambient environment, a high precision NTC thermistor is used to measure the ambient temperature of the thermopile. According to the pre-written standard temperature conditions: for example, the output voltage is measured when the object's temperature is 37℃ and the ambient temperature of the thermopile is 25℃. Then, by measuring the output voltage of the thermopile and the absolute temperature of the thermopile's ambient environment, the measured temperature is finally calculated by the CPU. Shiheng Electronics—— MF58 (100 k Ω 3950)temp-measurement NTC thermistor is commonly used, meanwile MF58 thermistor chips directly encapsulated together with the thermopile are also a great method. MF58 temp-measurment NTC thermistors have many advantages: high stability and reliability; wide range of resistance value and high precision; small size, light in weight, strong structure, easy automatic installation; fast thermal sensation, high sensitivity. MF58 products are widely used in home appliances, temperature detection or temperature compensation of office automation equipments, and in mobile phone batteries, battery packs, instrument coils, integrated circuits, quartz crystal oscillations and thermocouple/thermopole. MF58 products have passed, CQC, UL, C-UL , even through the most stringent UL standard of 100,000 durability tests, and through the AEC-Q200 test. They are trustworthy with reliable performance and superior quality.
  • 2. What are the types of thermistors?
    Thermistors are a class of sensing elements, which can be divided into positive temperature coefficient thermistors (PTC) and negative temperature coefficient thermistors (NTC) according to different temperature coefficients. The typical characteristic of thermistors is that they are sensitive to temperature, showing different resistance values at different temperatures. The positive temperature coefficient thermistor (PTC) has higher resistance value when the temperature is higher, and the negative temperature coefficient thermistor (NTC) has lower resistance value when the temperature is higher, they both belong to semiconductor devices.
  • 3. How to choose a thermistor? What should I pay attention to?
    Today, Shiheng electronics will explain to you. Positive temperature coefficient thermistor (PTC) is generally used in refrigerator compressor starting circuit, color picture tube degaussing circuit, motor overcurrent overheat protection circuit, current limiting circuit and constant temperature electric heating circuit. The commonly used thermistors in the compressor starting circuit are mz-01 ~ mz-04 series, MZ81 series, MZ91 series, MZ92 series and MZ93 series. According to different types of compressor to choose suitable for its starting thermistor, in order to achieve the starting effect. Color television, computer monitor used on the demagnetizing thermistor MZ71~MZ75 series. According to the working voltage (220V or 110V) of the TV set, the display, the working current and the specifications of the demagnetizing coil, the demagnetizing thermistor whose nominal resistance, maximum starting current and maximum working voltage meet the requirements can be selected. Low-power PTC thermistors for current limiting use include MZ2A~MZ2D series and MZ21 series, and PTC thermistors for motor overheat protection include MZ61 series. Models with nominal resistance value, switching temperature, working current and dissipation power that meet the requirements of the application circuit should be selected. Negative temperature coefficient thermistor (NTC) is generally used in a variety of electronic products for microwave power measurement, temperature detection, temperature compensation, temperature control and voltage stabilization. The commonly used NTC thermistors for temperature detection are MF53 series and MF57 series, and each series has a variety of models (the same type, different types of NTC thermistors, standard resistance values are also different) to choose from. MF21 series, RR827 series and so on are commonly used for voltage stabilizing NTC thermistors. The voltage stabilizing value and working current of thermistors can be selected according to the reference voltage designed by the application circuit. Common temperature compensation, temperature control with NTC thermistor MF11~MF17 series. Commonly used NTC thermistors for temperature measurement and temperature control include MF51 series, MF52 series, MF54 series, MF55 series, MF61 series, MF91~MF96 series, MF111 series, etc.The MF52 series and MF111 series NTC thermistors are suitable for temperature measurement and temperature control circuits in the temperature range from -80℃ to +200℃. The MF51 series, mf91-mf96 series NTC thermistors are suitable for temperature measurement and temperature control circuits below 300℃. MF54 series and MF55 series NTC thermistors are suitable for temperature measurement and temperature control circuits below 125℃. MF61 series and MF92 series NTC thermistors are suitable for temperature measurement and temperature control circuits above 300℃. When selecting a temperature control thermistor, attention should be paid to whether the temperature control range of the NTC thermistor meets the requirements of the application circuit. Nanjing shiheng electronic technology Co., Ltd. is a "national high-tech enterprise" registered in jiangning district, nanjing city, jiangsu province. The company focuses on the r&d, production and sales of a full series of NTC thermistors, NTC temperature sensors, Pt platinum resistance temperature sensors, PTC thermistors and zinc oxide varistors and other sensitive components. It is one of the leading manufacturers of semiconductor sensitive components in the domestic industry.
  • 4. Today, we would like to share with you the selection principle of thermistor?
    temperature sensor: Thermistors are a class of sensing elements, which can be divided into positive temperature coefficient thermistors (PTC) and negative temperature coefficient thermistors (NTC) according to different temperature coefficients. The typical characteristic of thermistors is that they are sensitive to temperature, showing different resistance values at different temperatures. The positive temperature coefficient thermistor (PTC) has higher resistance value when the temperature is higher, and the negative temperature coefficient thermistor (NTC) has lower resistance value when the temperature is higher, they both belong to semiconductor devices. Today, we would like to share with you the selection principle of thermistor? Nanjing shiheng electronic technology Co., Ltd. is a "national high-tech enterprise" registered in jiangning district, nanjing city, jiangsu province.The company focuses on the r&d, production and sales of the whole series of NTC thermistors, NTC temperature sensors, Pt platinum resistance temperature sensors, PTC thermistors and zinc oxide varistors and other sensitive components, is one of the leading manufacturers of semiconductor sensitive components in China.
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