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Bulletin AT-95026B page 1 of 4
2 and 2-1/2 in. (51 and 64 mm) Dial
■
Corrosion Resistant Polycarbonate Case
■
Indicating Gage and Limit Switch
■
Switch Can Activate Alarms and/or Shut
Down Equipment
■
Critical/High Temperature Limit Switch
Is Visible and Adjustable (Most Models)
■
Contact(s) Isolated From Ground
Description
The A20 Series (2 inch/51 mm dial) and the A25
Series (2-1/2 inch/64 mm dial) SWICHGAGE
®
mod-
els 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) thru
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 pol-
ished 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
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
Applications for A20 and A25 Series temperature
SWICHGAGE
®
instruments include: engines and
equipment in Oil Field, Marine, Irrigation
,
Construction
and Trucking industries. Monitoring Engine Coolant
temperature, Crankcase Oil, Transmission Oil.
Specifications
Dial: White on black; U.S.A. standard scale is dual
scale °F/°C; others available.
Case: Glass filled/Polycarbonate, corrosion-resis-
tant; 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, on page 2.
Maximum Temperature: See Temperature Ranges
and Factory Settings table on page 2.
Adjustable Limit Contact (A20T and A25T):
SPST contact; pilot-duty only, 2 A @ 30 VAC/
VDC; isolated from case ground. Normally 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 thru 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).
Base Models
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 20 and 25T 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.
Gage–Only Models
A20TG and A25TG MURPHYGAGE
®
Gage without contact(s).
*
For optional capillary lengths, engine adapters, sensing bulbs
and range combinations, see Murphy bulletin T-8428B.
**
Products covered by this bulletin comply with EMC Council
directive 89/336/EEC regarding electromagnetic
compatibility except as noted.
A20T Series
shown
**
AT-95026B
Revised 08-05
Catalog Section 10
A20 and A25 Series
Temperature SWICHGAGE
®