Thermostat (from the Greek. Therme – heat, heat; statos – standing, motionless), a device for maintaining a preset temperature. Thermostats call two groups of instruments: the finished product. For example, a laboratory thermostat to maintain set temperature for the cultivation of microorganisms; sensor that when a certain set temperature, enables or disables the actuator. Also thermostats are divided into two types – mechanical and electronic. In mechanical thermostats used mechanical (physical) properties of materials, such as changing the geometry of the material or its volume. Feature mechanical thermostat is that they do not have their own electricity.

The electronic thermostats used sensor, readings from which are read by an electronic circuit thermostat. Mercury thermostats are mercury thermostats one of the earliest types of thermostats, and now because of the toxicity of mercury are not used. There are two principles of mercury thermostats: mercury, rising to a height designated in thermometric vessel closes electrical contacts or impacts on some devices. The accuracy of the thermostat as high as 0,01 C. This thermostat is mainly used in industrial environments.

mercury sensor mounted on the bimetallic element, which is when the temperature changes its position or configuration and leads the mercury sensor. The accuracy of the thermostat was dependent on the accuracy of the bimetallic element and as high as 0,5 C. Thermostat used in both industrial and home environments. The bulb with mercury attached to the bimetallic element, a temperature-responsive and tilt the flask in one direction or another.