Mechanical Pressure Switchgage

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The 20DP and 25DP mechanical pressure switchgage series mechanism is enclosed in a steel case coated to resist corrosion. The A20DP and A25DP series have a polycarbonate case and are sealed from the environment. All feature a polycarbonate, break-resistant lens and a polished, stainless steel bezel to help protect these rugged, built-to-last instruments.


The mechanical pressure switchgage pointer acts as a pressure indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contacts have self-cleaning motion to ensure electrical continuity.


Additional features:

  • Constant visual indication of the condition of your filter is shown on the dial.
  • Two instruments in one with an accurate indicating gage and adjustable p.s.i.d. limit switch reduces inventory and installation time.
  • Adjustable contact lets you set the monitoring range of the gage. The contact is tamper proof and can be set only with a 1/16 Allen-head wrench.
  • All gages are made of durable materials allowing them to withstand rugged applications.
  • Early filter changes cost you money and increase the risk of contaminants entering the system. A Murphy filter restriction Swichgage instrument will let you know when to change the filter and maintain peak efficiency.


Base Models

20DP, 25DP, A20DP and A25DP Swichgage instrument
The gage pointer makes with an adjustable contact to complete a pilot-duty circuit.


20DPE, 25DPE, A20DPE and A25DPE Swichgage instrument
20DPE (was 20DPEO), 25DPE (was 25DPEO), A20DPE (was A20DPEO) and A25DPE (was A25DPEO).


Features an internal snap-acting SPDT switch, instead of the single pole/pointer contacts. When the switch closes on rising pressure, it becomes set, as pressure falls the switch resets. 20DPG, 25DPG, A20DPG and A25DPG Murphygage instrument gage without contact(s)




Dial: White on black, dual scale; U.S.A. standard scale is psi/kPa; U.K. standard scale is psi/bar.

Case: Polycarbonate/glass filled, corrosion-resistant; steel mounting clamp included

Bezel: Polished stainless steel, standard; others are available.

Pointer: Tempered nickel silver; Red tip.

Lens: Polycarbonate, high-impact.

Oil: Silicon Oil.


Temperature Range:

  • Ambient: -40°F (-40°C) thru 150°F (66°C).
  • Process: -40°F (-40°C) thru 250°F (121°C).


Process Connection: 1/8-27 NPTM brass.


Sensing Element: Beryllium copper diaphragm.


Gage Accuracy (% of Full Scale):

=300 psi (20 Bar) ±3% ±2% ±3%
400 psi (28 Bar) ±3% ±3% ±5%


Maximum Pressure: See Pressure Ranges and Factory Settings table.

Adjustable Limit Contact (A20P and A25P): SPST contact; pilot-duty only, 2A@30 VAC/DC; Closed when the low limit is met. 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: A20P: Number 4 screw terminals; A25P: Number 6 screw terminals


Snap-Switch Rating (A20PE and A25PE): SPDT, 3 A@ 30 VDC inductive; 4 A @ 125 VAC inductive


Wiring: A20PE: Number 4 screw terminals; A25PE: Number 6 screw terminals.


Unit Weight: A20 Series: 8 oz. (0.23 kg); A25 Series Models: 11 oz. (0.31 kg).


Unit Dimensions: A20 Series: 3 x 3 x 3 in. (76 x 76 x 76 mm); A25 Series Models: 4-3/4 x 4-3/4 x 2-3/4 in. (121 x 121 x 70 mm)