The Murphy 20TG-OS-320-16-1/2 thermostat belongs to the 20 series (with a 2-inch/51-mm dial).
It is a diaphragm-driven temperature indicator with a built-in electrical switch that can trigger alarms or turn equipment on/off. The gauge mechanism is enclosed in a steel housing coated with an anti-corrosion layer.
The polycarbonate shatter-proof lens and polished stainless steel dial help protect the instrument, making it sturdy and durable. This steam-driven vacuum gauge is equipped with sealed capillary tubes and a sensing bulb. When heated, the liquid in the sensing bulb vaporizes and exerts pressure on the diaphragm mechanism.
The diaphragm converts the steam pressure into mechanical dial readings. The gauge pointer also acts as a temperature indicator and a switch pole, completing the circuit when it contacts the adjustable limit contact.