Series A3000 Photohelic® Pressure Switch/Gage
3-in-1 Indicating Gage, Lo-limit and Hi-limit Control
Photohelic® Switch/Gages function as versatile, highly repeatable pressure switches combined with a precise pressure gage 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 (2.4) or 80 (5.5 bar) psig. Single pressure 36000S models measure to 6000 psig (413 bar) with a 9000 psig (620 bar) rating. Two phototransistor 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. Individual set point deadband is one pointer width - less than 1% of full scale. Set points can be interlocked to provide variable deadband - ideal for control of fans, dampers, etc. 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.
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
Models & Ordering
- GAGE SPECIFICATIONS
- Air and non-combustible, compatible gases.
- Wetted Materials:
- Consult Factory.
- ±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).
- Temperature Limits:
- 20 to 120°F. (-6.67 to 48.9°C). Low temperature option available.
- Process Connections:
- 1/8" female NPT.
- 4" (101.6 mm) dial face, 5" (127 mm) O.D. x 8-1/4" (209.55 mm).
- 4 lb (1.81 kg).
- SWITCH SPECIFICATIONS
- Switch Type:
- Each setpoint has 2 Form C relays (DPDT).
- ±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. Optional-EXPL explosion-proof enclosure does not possess any agency approvals.
- Bezel and front cover (with set point knobs and zero adjustment screw) removed to expose Photohelic® switch/gage set point mechanism.Cover is clear polycarbonate plastic.
- Gage pointer and light shutter are mounted on helix and balancing counterweight. Shutter passes through slot in optical limit switch to expose phototransistors to integral infrared light source or mask them depending on applied pressure.
- Light shield effectively protects phototransistors from strong outside light sources yet allows free pointer movement. It also gives interior a clean "finished" look.
- Optical limit switches are used for reliability and long service life. Attached directly to set pointers, they are individually aligned to assure precise switching accuracy.
- Semi-Flexible drive shaft connects to set point knobs.
- Zero adjustment screw connects to screw in cover to adjust zero pressure reading.
- Plastic enclosure protects electronic components and electrical connections.
- Polycarbonate connection or terminal board is self-extinguishing.
- Glass epoxy printed circuit boards for durability and permanence.
- Load relays are DPDT with latching feature for maximum application versatility.
- Electronics are designed to operate on 50/60 Hz, 120 volt current with 10% over or under voltage. Special units for other voltages are available.
- Switch set pointers show switch settings at all times.
- Spring loaded friction clutch prevents operator damage of set point mechanism.
- -SR Single contact, right set point, for actuation on increasing or decreasing pressure.
- -OLS OEM Model, less relay and transformer components and housing but including infared diodes and phototransistor(s), light shutter and set pointer(s). For single or double contact.
- -RMR Remote-Mounted Relay, relay pack may be mounted remotely from gage. Standard length is 5 ft. For other lengths, specify cable length required.
- -TAMP Tamper-proof knobs, low temperature option, special scales, voltages and other features and modifications are available.
- Special Housings available include Weatherproof (NEMA 4) and Explosion-proof (NEMA 7 & 9; NEC Cl I, Gr C&D; Cl II, Gr E, F&G; Cl III). Contact Customer Service for detailed dimension drawings.
- Scale No. 3401 Square Root Specify Range.
- Scale No. 3402 Blank Scale Specify Range.
- High & Low Latching Circuits. Dwyer Photohelic® switch/gages can be wired for high-latching, low-latching or combination high-low latching circuits. That is, the equipment will hold in these respective positions once activated and until manually reset. This can be particularly useful for alarm and signal applications where control is accomplished by another Photohelic® switch/gage or other means. Complete wiring and operational instructions are included. Where manual reset is required a dry circuit push button such as Dwyer Part A-601 should be used.
|Model Number||Description||Usually Ships||Price||Order|
|A-601||Manual reset switch.||Next Day||$39.00||Order|
|A-298||Flat aluminum bracket for flush mounting Photohelic® & Capsuhelic® gages, 603A, 605, and 3000MR.||Next Day||$27.75||Order|
|EXAMPLE||A3000-00N||24VAC||Series A3000-00N-24VAC Photohelic® Pressure Switch/Gage, range .05-0-0.2" w.c., with 24VAC relay pack.|
0-.25" w.c. & 300-2000 FPM AV
0-.5" w.c. & 500-2800 FPM AV
0-1" w.c. & 500-4000 FPM AV
0-2" w.c. & 1000-5600 FPM AV
0-10" w.c. & 2000-12500 FPM AV
0-6 mm w.c.
0-10 mm w.c.
0-20 mm w.c.
0-25 mm w.c.
0-50 mm w.c.
0-80 mm w.c.
0-100 mm w.c.
0-150 mm w.c.
0-200 mm w.c.
0-250 mm w.c.
0-300 mm w.c.
0-500 mm w.c.
0-5000 mm w.c.
10-0-10 mm w.c.
15-0-15 mm w.c.
0-200 mm Hg
0-1 cm w.c.
0-2 cm w.c.
0-5 cm w.c.
0-8 cm w.c.
0-10 cm w.c.
0-15 cm w.c.
0-20 cm w.c.
0-25 cm w.c.
0-30 cm w.c.
0-40 cm w.c.
0-50 cm w.c.
0-80 cm w.c.
0-100 cm w.c.
0-150 cm w.c.
0-200 cm w.c.
0-250 cm w.c.
0-300 cm w.c.
2-0-2" cm w.c.
5-0-5 cm w.c.
10-0-10 cm w.c.
15-0-15 cm w.c.
24 VAC Relay Pack
220/240 VAC Relay Pack
Certificate of Origin
Energizing (set point low: de-energizing/energizing; set point high: energizing/de-energizing)
Energizing (set point low: energizing/de-energizing; set point high: energizing/de-energizing)
Energizing (set point low: energizing/de-energizing; set point high: de-energizing/energizing)
Energizing (set point: energizing/de-energizing)
Explosion-proof Housing with Breather & Drain
Green Scale Overlay
Horizontal Calibration (90° face up)
Latching Option (high/low)
Latching Option (low/high)
Latching Option (low/low)
Mirror Scale Overlay
NIST Certificate of Calibration
Red Scale Overlay
Remote Mounted Relay Std. 5 Ft.
Remote Mounted Relay 1 Ft.
Remote Mounted Relay 2 Ft.
Remote Mounted Relay 3 Ft.
Remote Mounted Relay 10 Ft.
Remote Mounted Relay 15 Ft.
Remote Mounted Relay 20 Ft.
Remote Mounted Relay 25 Ft.
Remote Mounted Relay 30 Ft.
Remote Mounted Relay 40 Ft.
Remote Mounted Relay 50 Ft.
Remote Mounted Relay 60 Ft.
Remote Mounted Relay 70 Ft.
Remote Mounted Relay 80 Ft.
Remote Mounted Relay 90 Ft.
Remote Mounted Relay 100 Ft.
Single Right Hi Latching
Single Right Lo Latching
Stainless Steel Tag
Tilt Angle from Vertical in Degrees (-90 to 90)
Yellow Scale Overlay
- What restrictions, if any, are imposed for the Magnehelic® and Photohelic® gages in vacuum service?
- In applications involving higher vacuums than 20" Hg, leakage due to gage housing porosity becomes the limiting factor.
- Are air velocity scales available?
- Yes, the information we require to supply the proper range is the velocity (fpm or m/s) or velocity pressure (inches of water or kpa) and density of air (lb/ft3 or g/cm3).
- What is the NEMA rating of a Photohelic®?
- Our standard is considered to be NEMA 1 rated for general purpose. We do have weatherproof (NEMA 4X) and explosion-proof (NEMA 7 & 9) enclosures available.
- What is an RMR Photohelic®?
- The RMR option is for a remote mounted relay, where the relay pack is seperate from the gage. The unit comes with a standard interconnecting cable that is 3 feet long.
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