Multimeter to measure the quality of the thermostat

　　Multimeter to measure the quality of the thermostat

　　Thermostats are divided into two categories: heating thermostats and cooling thermostats. The measurement methods after removal are described as follows:

　　1. Measure the (heat control) thermostat used for household shower water heaters: Set the multimeter to the resistance range, measure the two plugs of the thermostat, rotate the temperature adjustment handle to close the contacts, the multimeter indicates that it is on, insert the temperature control probe into boiling water (or heat it with a lighter), you will hear a click from the thermostat and the contacts will be disconnected, and the multimeter will show disconnection, which proves that the thermostat is good.

　　2. Use the above method to measure the (cold control) thermostat of the freezer: manually adjust the thermostat to the minimum, measure the two plugs of the thermostat at room temperature, they should be connected, put the thermostat into the freezer of the refrigerator and freeze it for about 10 minutes (or use a fluorine bottle to quickly spray fluorine on the temperature sensing head), the thermostat contacts should be disconnected with a click, and the multimeter should also show disconnection, the temperature control is good.

　　Note: Be careful during actual operation to avoid damaging other parts.

　　How to judge whether the thermostat is good or bad

　　How to judge whether the thermostat is good or bad: remove the suspected faulty thermostat from the box, rotate the thermostat adjustment rod to the normal position, and use the multimeter R×l gear to measure the resistance between the two main contacts of the thermostat. The normal resistance should be zero or 1-2Ω. If the resistance is infinite, it means that the temperature sensing agent in the temperature sensing element has leaked out; if the resistance is above 10Ω, it means that there is serious carbon accumulation between the contacts. Put the thermostat with normal resistance into the freezer of a small refrigeration equipment such as a refrigerator or freezer that is operating normally for about 10 minutes, and then use the multimeter R×l gear to quickly measure the resistance between the two main contacts of the thermostat. Under normal circumstances, it should be infinite. If the resistance is zero, it means that the contacts are sticking. If the thermostat contacts are not sticking, hold the thermostat's temperature sensing tube with your hand, and then measure the resistance between the two main contacts. When you hold the temperature sensing tube, the two contacts are quickly connected, and the indication value of the multimeter changes from infinite resistance to zero resistance, which means that all mechanisms of the temperature controller are working normally.