N°5 – Stats (VTC to A level)

Stats are simple control mechanisms which compactly regroup the 4 stages of a control regulation system (measurement-comparison-transmission-action).

Their mode of action is often the equivalent of a basic “open/close” electrical contact. This method of control is called “all or nothing.”

So:
The regulating of a heating system by ambient thermostats can mean a succession of on/off actions of the boiler.

• It’s too hot, the electric contact of the thermostat opens and the boiler stops.
• It’s too cold, the electric contact of the thermostat closes and the boiler starts.

Stats are used in simple control systems, especially in the field of safety.
There are thermostats (general temperature regulating), aquastats (water temperature), pressostats or manostats (pressures), and hygrostats (humidity), etc.

There are mechanical and more precise electronic models.
In mechanical ambient thermostats and aquastats, detection is carried out by a temperature sensitive device; the comparison is carried out by a balance spring and the action carried out by an opening or closing of an electric circuit.