The 20 Series (2 inch/51 mm dial) and the 25 Series (2- 1/2 inch/64 mm dial) Swichgage models are diaphragmactuated, temperature-indicating gages with built-in electrical switches for tripping alarms and/or shut-down devices.
Ranges are available from 32°-120°F (0°-45°C) through 300°-440°F (160°-220°C).
The gage mechanism is enclosed in a steel case coated to resist corrosion. A polycarbonate, breakresistant lens and a polished, stainless steel bezel help protect this rugged, built-to-last instrument. These vapor-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 the diaphragm mechanism. The diaphragm translates this vapor pressure into a mechanical gage reading.
For series 20T and 25T, 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 grounded through the Swichgage case. They have a self-cleaning motion to enhance electrical continuity.
Models 20TE and 25TE have internal snap-acting SPDT switches. Gage-only models without contacts (MurphyGage® instrument) are also available.
These instruments are used on industrial engines and equipment in oil field, marine, irrigation, construction and trucking industries and for monitoring engine coolant, crankcase oil and transmission oil.