How to test a bimetal thermal switch?

 Before you start to test a thermal switch, a test oven has to be ready.

1. The test oven should be specially designed for temerature testing. It must have the following functions:

1.1      The internal temperature of oven should be even and stable. The temperature difference between any two points should be less than 1℃;

1.2      The temperature rise speed of oven must be under control. Before the temperature inside of oven reaches the 10℃ lower than bottom limit of rated temperature tolerance value, the oven can run under full load and the fast temperature rise speed is acceptable. Once the temperature reaches the level, the speed has to be controlled at or lower than 1℃ per 2 minutes.

2.  After making sure that the oven has the right function, you can install the thermal switch to the test oven. The body of thermal switch should contact the testing facility tightly and effectively. The circuit connection should be workable. If there is a temperature sensing head or thermocouple inside of the equipment, it should be mounted on the effective position.

3.       Then, close the test circuit and the oven starts to work. If the test oven is equipped with a electronic recorder, the test curve would be recorded. If no, you have to prepare a notepad to write all data down, at least 10 cyclings should be recorded, both OFF and ON temperature.

4.  Analyzing the test data and check if the thermal switch can function properly. If the quality is good, the test curve after initial 2 cycles should be uniform. If no, the curve would have variaties.

5. All test equipment like oven, thermocouple and meters should be calibrated regularly, to ensure the reliable function.