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.
Coolant or Oil Temperature
A20T and A25T Series Swichgage: For these models the gage pointer makes with an adjustable contact to complete a pilot-duty circuit.
A20TL and A25TL Swichgage: For use on Ford Worldwide engines. Supplied with special sensing bulb.
A20TE and A25TE Swichgage: A20TE (was A20ESR) and A25TE (was A25ESR). Models with internal SPDT snap-switches, instead of the single pole/pointer contact(s). When the switch closes on rising temperature, it becomes set. As temperature decreases the switch resets.
Model A25TE is CSA listed for non-hazardous areas.
Model A25TE-EX is CSA listed for Class I, Division 1,
Groups C & D hazardous areas.
A20TABS and A25TABS Swichgage: Same as A20 and A25T with internal SPDT snap-switch for pre-alarm.
Cylinder Head Temperature
A20TH and A25TH Swichgage: A20TH (was A20TL8133) and A25TH (was A25TL8133). For use on air-cooled engines.
A20TG and A25TG Murphygage: Gage without contact(s).
- Dial: White on black; U.S.A. standard scale is dual scale °F/°C; others available
- Case: Glass filled/Polycarbonate, corrosion-resistant; steel mounting clamp included
- Bezel: Polished stainless steel, standard; others are available.
- Pointer: Tempered nickel silver; red tip
- Lens: Polycarbonate, high-impact
- Sensing Element: Beryllium copper diaphragm
- Capillary: PVC armored copper; 4 ft. (1.2 m).* Stainless steel armor optional
- Sensing Bulb: Copper*
- Gage Accuracy: See accuracy chart
- Maximum Temperature: See Temperature Ranges and Factory Settings table
- Maximum Ambient Temperature: -40°F (-40°C) through 150°F (66°C)
- Adjustable Limit Contact (A20T and A25T):
- SPST contact; pilot-duty only, 2 A @ 30 VAC/VDC; isolated from case ground
- Closed when the high limit is met. Normally Open when pointer is in normal operating range. Contacts are gold flashed silver.
- Limit Contact Adjustment: by a 1/16 in. hex wrench through 100% of the scale.
- Wiring: A20T: Number 4 screw terminals; A25T: Number 6 screw terminals.
- Snap-Switch Rating (A20TE and A25TE):
- SPDT, 3 A@ 30 VDC inductive; 4 A @ 125 VAC inductive
- Wiring: A20TE: Number 4 screw terminals; A25TE: Number 6 screw terminals
- Unit Weight: A20 Series: 11.9 oz. (0.370 kg); A25 Series Models: 13.3 oz. (0.413 kg)
- Unit Dimensions: A20 Series: 4-3/4 x 4-3/4 x 3 in. (121 x 121 x 76 mm); A25 Series Models: 4-3/4 x 4-3/4 x 2-3/4 in. (121 x 121 x 70 mm)
*For optional capillary lengths, engine adapters, sensing bulbs and range combinations, see Murphy bulletin 8428.
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