A coil thermometer is a sensor that measures the temperature of a motor or transformer winding. It is based on the property that the resistance of a coil varies with temperature, and the temperature of the winding is inferred by measuring the coil resistance.

Working Principle: The coil thermometer utilizes the relationship between coil resistance and temperature to measure the winding temperature. Normally, the resistance of a coil increases with temperature. The coil thermometer converts the resistance value to the temperature value by measuring the resistance value of the coil and utilizing the temperature coefficient of the coil material.

. Temperature Measurement Principle: Coil thermometers typically use a platinum (Pt) coil. Platinum coils are a stable material with linear temperature characteristics. Based on the relationship between the resistance of the platinum coil and the temperature, the coil resistance value can be converted to a temperature value using resistance-temperature conversion equations (such as the international standard PT100 and PT1000 curves).


Sensor type: Coil thermometers can be categorized into two types: direct measurement type and indirect measurement type.

   - Direct measurement type: Direct measurement type coil thermometer is the sensor coil is installed directly on the surface of the winding to be measured temperature. It can measure the temperature of the winding in real time, but needs to be installed to ensure good contact between the sensor and the winding.

   - Indirect Measurement Type: Indirect measurement type coil thermometers install the sensor coil near the winding, measure the ambient temperature, and then infer the winding temperature through heat conduction. This method avoids direct contact with the winding, but requires heat transfer calculations to estimate the winding temperature.

Advantages and Applications: Coil thermometers offer the following advantages and applications:

   - High accuracy: Coil thermometers provide high accuracy in temperature measurement, especially in the high temperature range.

   - Fast Response: Coil thermometers have a fast response time and are able to detect temperature changes quickly.

   - Long life: Coil thermometers typically have a long life and stability.

   - Wide range of applications: coil thermometers are widely used in motors, generators, transformers, power equipment and other fields for monitoring and controlling the winding temperature to ensure the normal operation and safety performance of the equipment.

The accuracy and measurement precision of coil thermometers are affected by a variety of factors, such as the characteristics of the coil material, the quality of the contact between the coil and the winding, and the ambient temperature. When using coil thermometers, it is necessary to select the appropriate type of sensor, installation method, and proper calibration and compensation according to the specific requirements to ensure the accuracy and reliability of the measurement results.

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