The 20T-300-8-1/2 is a part of the 20 Series (2 inch/51 mm dial) Swichgage models which are diaphragm-actuated, temperature-indicating gauges, with built-in electrical switches for tripping alarms and/or shutdown devices. Ranges from 300-440°F (160-220°C).
The gauge mechanism is enclosed in a steel case coated to resist corrosion. A polycarbonate, break resistant lens and a polished, stainless steel bezel help protect this rugged, built-to-last instrument. These vapour actuated gauges feature a sealed capillary tube and a sensing bulb. When subjected to heat, the liquid in the sensing bulb changes to vapour creating pressure against the diaphragm mechanism. The diaphragm translates this vapour pressure into a mechanical gauge reading.
For series 20T, the gauge pointer acts as a temperature indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contact(s) are grounded through the Swichgage case. They have self-cleaning motion to enhance electrical continuity.
Contact form description.