The temperature sensor is used to automatically sample and monitor the ambient temperature. When the ambient temperature is higher than the control set value, the control circuit starts and the control hysteresis can be set. If the temperature is still rising, when the temperature exceeds the set limit alarm temperature, the over-limit alarm function is activated. When the controlled temperature cannot be effectively controlled, in order to prevent the equipment from being destroyed, the device can be stopped by the tripping function. Mainly used in a variety of high and low voltage switchgear, dry-type transformers, box-type substations and other related areas of temperature use.