Dwyer AT3A3000 Photohelic® Pressure Switch / Gages

Dwyer AT3A3000 Photohelic Switch/Gages functions as versatile, highly repeatable pressure switches combined with a precise pressure gauge employing the time-proven Magnehelic® gage design. The Photohelic® switch/ gage measures and controls positive, negative, or differential pressures of air and compatible gases. Standard models are rated to 25 psig (1.7 bar) with options to 35 psig (2.4 bar) or 80 psig (5.5 bar).

Two phototransistors actuated, DPDT relays are included for low/high limit control. Easy to adjust set point indicators are controlled by knobs located on the gage face (accessible opening case after de-energizing instrument). Set points can be interlocked to provide variable dead band– ideal for control of fans, dampers, etc

Dwyer AT3A3000 Photohelic Features

  • 3-in-1 ATEX approved instrument allows the reduction of several instruments with one product, saving inventory, installation time and money
  • Flame-proof ATEX enclosure with optional glass window and aluminum housing protects the device in hazardous areas while giving local visibility to process pressure and set point status


  • Hazardous area pressure measurement and switching
  • Air conditioning systems
  • Clean rooms
  • Fume exhaust systems

Important Notes for Installation

  • Cables must be fitted through 1/2″ NPT cable gland or ATEX/IECEx conduit (not supplied with instrument).
  • Make sure after cabling to close tight cover and cable gland, in order to keep IP66 rating (IP65 with option OPV, overpressure relief valve).
  • Open cover only after de-energizing instrument.
  • Attention: Check local safety rules and warnings on unit and manual for a correct use of the instrument in hazardous area.

Dwyer AT3A3000 Photohelic Specification

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 in Hg to 25 psig (-0.677 to 1.72 bar). MP option; 35 psig (2.41 bar), HP option; 80 psig (5.52 bar).
Temperature Limits 20 to 120°F (-6.67 to 48.9°C) LT low temperature option to -20°F available; (Note: Product temperature limits differ from case).
Dial Size 4″ (101.6 mm).
Mounting Orientation Diaphragm in vertical position
Set Point Adjustment Adjustable knobs on Photohelic® gage face behind enclosure cover. Follow instructions and safety warnings to open cover.
Switch Specifications
Switch Type Each setpoint has 2 Form C relays (DPDT).
Repeatability ±1% of FS.
Electrical Rating 10 A @ 120 VAC, 6 A @ 240 VAC, 60 Hz res. 10 A @ 28 VDC.
Electrical Wiring Screw terminals.
Power Requirements 120 VAC, 50/60 Hz; 240 VAC & 24 VAC power optional.
Enclosure Rating IP66. IP65 with option OPV, overpressure relief valve.
Housing material Aluminum.
Finishing Texture epoxy coat RAL7038.
Pressure Connections 1/8″ NPT female brass (SS optional). In presence of acetylene it is necessary to use SS.
Electrical Connections Three 1/2″ FNPT. Cable gland not included.
Weight 28.4 lb (12.9 kg).
ATEX Certificate BVI 14ATEX0072.
Agency Approvals TEX Compliant CE 1370 Ex II 2G Ex d IIC T6 Gb / II 2D Ex tb IIIC T85°C Db, -60°C=Tamb=+60°C IECEx Compliant: Ex d IIC T6 Gb / Ex tb IIIC T85°C Db

Download Data Sheet: Series AT3A3000 Photohelic® Switch Gages

Ref: dwyer-inst.com

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