The A20 Series (2 inch/51 mm dial) and the A25 Series (2-1/2 inch/64 mm dial) Swichgage models are diaphragm-actuated, temperature-indicating gages, with built-in electrical switches for tripping alarms and/ or shutdown devices.
Ranges are available from 32°-120° F (0°-45° C) through 300°-440° F (160°-220° C).
All models of these rugged, built-to-last instruments are fully sealed from the environment by the unique combination of a polycarbonate case and lens, a polished stainless steel bezel and O-ring seals. These vapor/pressure actuated gages feature a sealed capillary tube and a sensing bulb. When subjected to heat, the liquid in the sensing bulb changes to vapor creating pressure against a diaphragm mechanism. The diaphragm translates this vapor pressure into a mechanical gage reading.
For series A20T and A25T, the gage 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 isolated from ground. They have a self-cleaning motion to enhance electrical continuity. Models A20TE and A25TE have internal snap-acting SPDT switches.
Gage-only models, without contacts (MurphyGage®) are also available.
Applications for A20 and A25 Series temperature Swichgage instruments include: engines and equipment in the oil field, marine, irrigation, construction and trucking industries, monitoring engine coolant temperature, crankcase oil, transmission oil.