Difference between Temperature Power Sensor and Disk Type Thermostat



	Operating Principle of Temperature Power Sensor					Operating Principle of Disk Type Thermostat
	Bimetal thermostats for precise control applications specifically designed and built with miniaturization and low cost in mind. Each consists essentially of a spring, which has virtually indefinite service life and sharp, distinctive tripping characteristics, and a flat bimetal which is distortion free. Two pieces of bimetal are used in combination to increase sensitivity. The small differential, sharp snap action spring plays an important role in achieving desirable thermostatic response. This snap spring turns on and off over an exceptionally small distance (approx. 0.05m/m), or in terms of temperature, approx. 3 degrees Beryllium bronze snap spring can withstand at least 2 million operations.					By forming a bimetal strip into a dome shape (hemispherical, dished shape) to acquire snap action, the disk type thermostat is characterized by its simplicity of construction. The simple design facilitates volume production and, because of its low cost, account for 80% of the entire bimetallic thermostat market in the world. However, the bimetallic material has physical properties similar to ordinary steel material and is not a spring material in itself. During the course of repeated tripping, it is no wonder that just a strip of ordinary metal, formed into a dome, will progressively distort, or lose its shape, and return to its original shape of a flat strip. The life of this style of thermostat is generally limited to several thousand to tens of thousands of operations at best. Although they demonstrate almost ideal characteristics as protectors, they fall short of being qualified to serve as controllers.

Characteristics of Temperature Power Sensor and Disk Type Thermostat
	Temperature Power Sensor (controller)	Disk Type Thermostat (protector)
Life	100 thousand operations at the rated load (with no operational temperature change) 5 million operations at the small load (with no operational temperature change)	20~30 thousand times for a controller (within 5% operational temperature change) 100 thousand times for a protector (in a range where the device functions normally)
Differentials	For entire temperature range(–10°C~110°C) rankA : 2~4degrees rankB : 3~6degrees rankC : 5~8degrees rankD : approx.10degrees	–20°C~100°C········10degrees 100°C~150°C········20degrees 150°C~200°C········30degrees 200°C~250°C········40~50degrees
Contact capacity	MQT8 Series : 125V/2A M2 & M3 Series : 125V/5A	1/2 inch disk: 125V/15A
Contact configuration	OFF when temperature rises ON when temperature rises A transfer contact available	OFF when temperature rises ON when temperature rises

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