There are many types of ptc thermistors. As a temperature measurement, there are usually glass-sealed type epoxy type small head enameled wire type. As the temperature measuring part of the induction cooker, glass sealed type and other accessories are usually used to form thermistors. Components, negative temperature coefficient thermistor, namely NTC thermistor, room temperature resistance is about 100k, and 10K 50K specifications, but more use 100K, the error is greater than ± 1%, NTC thermal resistance decreases with increasing temperature. The figure below shows the temperature sensor probe of the induction cooker thermistor. In actual use, the ptc thermistor is in close contact with the ceramic board, and thermal grease is applied at the contact point to improve the control sensitivity.
Induction cooker temperature measurement generally adopts A / D port detection, and now many chips have A / D detection function. The ptc thermistor is connected in series with another resistor. The principle of the resistor divider is used to read the AD value. Finally, the current temperature is compared with the value obtained by dividing by the voltage. The thermistor of the induction cooker not only plays the role of temperature measurement, but also in order to ensure safety, when the temperature reaches a certain value, the circuit automatically cuts off the output. When the thermistor is abnormal (such as short circuit or open circuit), the general manufacturer will display the corresponding error code. It is convenient to find out the reason.
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