Series A3000 Photohelic ® Pressure Switch/Gage

Gage reading is continuous and unaffected by switch operation, even during loss of electrical power. Choose from full scale pressure ranges from a low 0-.25″ (0-6 mm) w.c. up to 30 psi (21 bar); single positive pressure to 6000 psig (413 bar).

Photohelic Sensing – How It Works
In typical applications, these Dwyer switch/gages control between high and low pressure set points. When pressure changes, reaching either set point pressure, the infrared light to the limiting phototransistor is cut off by the helix-driven light shutter. The resulting phototransistor signal is electronically amplified to actuate its DPDT slave relay and switching occurs. Dead band between make and break is 1% of full scale or less – just enough to assure positive, chatter-free operation.

Relay-Transformer Features
A plastic housing protects all electronic components. Solid-state and integrated circuit electronics are on glass-epoxy printed circuit boards and self-extinguishing terminal boards.

Please see SERIES AT3A3000 for ATEX approved.

• Air Conditioner Systems

• Clean Rooms

• Fume Exhaust Systems





  • Service: Air and non-combustible, compatible gases.
  • Wetted Materials: Consult Factory.
  • Accuracy: ±2% of FS at 70°F (21.1°C). ±3% on -0 and ±4% on -00 models.
  • Pressure Limits: -20″ Hg. to 25 psig (-0.677 to 1.72 bar). MP option; 35 psig (2.41 bar), HP option; 80 psig (5.52 bar). 36003S – 36010S; 150 psig (10.34 bar). 36020S and higher; 1.2 x full scale pressure.
  • Temperature Limits: 20 to 120°F. (-6.67 to 48.9°C) Low temperature option available.
  • Process Connections: 1/8″ female NPT.
  • Size: 4″ (101.6 mm) dial face, 5″ (127 mm) O.D. x 8-1/4″ (209.55 mm).
  • Weight: 4 lb (1.81 kg).


  • Switch Type: Each setpoint has 2 Form C relays (DPDT).
  • Repeatability: ±1% of FS.
  • Electrical Rating: 10A @ 28 VDC, 10A @ 120, 240 VAC;
  • Electrical Connections: Screw terminals. Use 167°F (75°C) copper conductors only.
  • Power Requirements: 120 VAC, 50/60 Hz; 240 VAC & 24 VAC power optional.
  • Mounting Orientation: Diaphragm in vertical position. Consult factory for other position orientations.
  • Set Point Adjustment: Adjustable knobs on face.
  • Agency Approvals: CE, CSA, UL. NOTE: Optional (-EXPL) Explosion-proof Enclosure does not possess any agency approvals.