Thermostats are an integral part of nearly every form of heating equipment, whether industrial or domestic.
Industrial thermostats must be reliable and robust over far greater operational ranges, environmental conditions, and usually be easily replaceable, all at a reasonable cost. Mechanical designs still commonly in use today are proven over decades and there is no sign of these instruments becoming obsolete.
Electronic thermostats are usually a combination of a simple controller and either PT100 or RTD sensor.
Maclaren ThermostatMaclaren Thermostat Data Sheet HERE