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Dwyer Series AT2DH3

ATEX Approved DH3 Differential Pressure Controller

Dwyer  Series AT2DH3 Digihelic
Dwyer Series AT2DH3 Digihelic

Digihelic® Pressure Control in Flame-Proof ATEX Enclosure

The Dwyer Series AT2DH3 ATEX Approved DH3 Digihelic Differential Pressure Controller is a 3 in 1 instrument possessing a digital display gage, control relay switches, and a transmitter with current output. Combining these three features allows the reduction of several instruments with one product, saving inventory, installation time and money. The ATEX approved Digihelic® controller is the ideal instrument for hazardous area pressure, velocity and flow applications by allowing for the selection of pressure, velocity or volumetric flow operation in several commonly used engineering units. Two SPDT control relays with adjustable dead bands are provided along with a scalable 4 to 20 mA process output. In velocity or flow modes, a square root output is provided on the 4 to 20 mA signal to coincide with the actual flow curve. Flame-proof ATEX enclosures are available in aluminum and can include a glass window for viewing process information and set point status on digital display.

Important notes for installation:
• Cables must be fitted through 1/2″ NPT cable gland or ATEX 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.


  • Service:Air and non-combustible, compatible gases.
  • Wetted Materials:Consult factory.
  • Housing Material:Die cast aluminum case and bezel.
  • Accuracy:< 5 in w.c. (except ±2.5 in w.c.): ±1%; All other ranges: ±0.5% at 77°F (25°C) including hysteresis and repeatability (after 1 hour warm-up).
  • Stability:< ±1% per year.
  • Pressure Limits:Ranges ≤ 2.5 in w.c.: 25 psi; ±2.5″, 5 in w.c.: 5 psi; 10 in w.c.: 5 psi; 25 in w.c.: 5 psi; 50 in w.c.: 5 psi; 100 in w.c.: 9 psi.
  • Temperature Limits:32 to 140°F (0 to 60°C) Case: -76 to 140°F (-60 to 60°C) (Note: Product temperature limits differ from case).
  • Compensated Temperature Limits:32 to 140°F (0 to 60°C).
  • Thermal Effects:0.020%/°F (0.036/°C) from 77°F (25°C).
  • Power Requirements:12 to 28 VDC, 12 to 28 VAC 50 to 400 Hz.
  • Power Consumption:3 VA max.Output Signal:4 to 20 mA DC into 900 ohms max.
  • Zero & Span Adjustments:Accessible via menus in safe zone only.
  • Response Time:250 ms (damping set to 1).
  • Display:Backlit 4 digit LCD 0.4″ height LED indicators for set point and alarm status.
  • Electrical Wiring:Screw terminal.
  • Mounting Orientation:Mount unit in vertical plane.
  • Dial Size:5″ (127 mm) OD x 3-1/8″ (79.38 mm).


  • Switch Type:2 SPDT relays.Electrical Rating:1 amp @ 30 VAC/VDC.
  • Set Point Adjustment:Adjustable via keypad on face in safe zone only.
  • 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: Two 1/2″ FNPT. Cable gland not included.
  • Weight: 12.3 lb (5.6 kg).
  • ATEX Approved Products from Comhas with ECN: BVI 14ATEX0072.
  • Agency Approvals: CE 1370 II2 GD Ex d IIC Gb T6; -60°C ≤ Ta ≤ +60°C Ex tb IIIC Db T 85°C.