Dimensional Enlargement
Both Photohelic® and Capsu-Photohelic® Switch/Gages function as versatile, highly repeatable pressure switches combined with a precise pressure gage employing the time-proven Magnehelic design®. The lower cost Photohelic measures and controls positive, negative or differential pressures of air or compatible gases (single positive pressure only on 36000S models). Standard units are rated to 25 psig; optional are 35 or 80 psig construction. The Capsu-Photohelic is designed with an encapsulated pressure sensing element allowing use for liquid as well as gas service at pressures to 500 psig. An optional cast brass case is available for water or water based liquids.

Two phototransistor actuated, DPDT relays are included for low/high limit control. Easy to adjust setpoint indicators are controlled by knobs located on gage face. Individual setpoint deadband is one pointer width - less than 1% of full scale. Setpoints can be interlocked to provide variable deadband - ideal for control of fans, dampers, pumps, 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" w.c. up to 300 psi; single positive pressure to 6000 psig.

 
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 translucent Styrene Acrylonitrile housing protects all electronic components. Solid-state and integrated circuit electronics are on glass-epoxy printed circuit boards and self-extinguishing terminal boards.

APPLICATIONS - PHOTOHELIC SWITCH/GAGES
In both series of pressure switch/gages, you get the convenience of a visual indication plus high-low limit switching. For both OEM and in-plant applications, the Photohelic switch/gage is used to control pressures in air conditioning systems, clean rooms, fluidic and pneumatic control systems, materials handling equipment; alarm or control fume exhaust systems; control pressure in air structures and monitor respiratory and blood pressures.

STANDARD MODEL
Two phototransistor-actuated circuits and two DPDT relays permit both high and low alarms or limit controls. Relays are de-energized when gage pointer is to the left of respective set points; relays are energized as pointer passes to the right of set points. Loss of electrical power or loss of pressure provide "fail safe" protection.

OPTIONS
Single contact, right set point, for actuation on increasing or decreasing pressure.
OEM Model, less relay and transformer components and housing but including phototransistor(s), light shutter and set pointer(s). For single or double contact.
Remote-Mounted Relay, relay pack may be mounted remotely from gage. Specify cable length required.
Tamper-proof knobs, low temperature option, special scales, voltages and other features and modifications are available.
Special Housings available include Weatherproof (NEMA 4X) 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.

HIGH AND 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. 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.

 
PHYSICAL DATA
Ambient Temperature: 20 to 120°F. (-6.7 to 49°C) LOW temperature option available.
Rated Pressure: Photohelic, -20" Hg. to 25 psig (-.67 to 1.7 bar). MP option; 35 psig (2.4 bar), HP option; 80 psig (5.5 bar). 36003S-36010S; 150 psig (10.3 bar). 36020S and higher; 1.5 x full scale pressure. Capsu-Photohellic, -20" Hg. to 500 psig (-.67 to 34.4 bar).
Accuracy: Photohellc, ±2% of full scale at 70°F (21 .1°C). 3% on -0 and 4% on -00 models. Capsu-Photohelic, ±3% of full scale at 70°F (21.1°C). 2% on 43000S models; 4% on 43215, 43220 and 43500. Gage Connections: Photohelic, 1/8" NPTF. Capsu-Photohellc, 1/4" NPTF.
Power Required: 120 VAC, 50/60 Hz
Electrical Rating of Relays: 10A @ 120 VAC, 6A @ 240 VAC, 60 Hz res.
Conduit Opening: 3/4" conduit.
Finish: Baked, dark gray hammerloid.
Weight: Photohelic, 4 lbs. (1.8 kg). Use with air or compatible gases only. Capsu-Photohelic, 5 Ibs., 12 OZ. (2.6 kg). Use with air or compatible gases or liquids. Brass case required for water or water based liquids.

 
Check these features for dependable control
  1. Bezel and front cover with set point PHOTOHELIC model shown. knobs and zero adjustment screw removed to expose Photohelic set point mechanism. Cover is clear polycarbonate plastic.
  2. 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
  3. Light shield effectively protects phototransistors from strong outside light sources yet allows free pointer movement. It also gives interior a neat "finished" look.
  4. 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.
  5. Flexible drive shaft connects to set point knobs.
  6. Zero adjustment screw connects to screw in cover.
  7. Styrene acrylonitrile enclosure protects electronic components and electrical connections.
  8. Polycarbonate connection or terminal board is self-extinguishing.
  9. Glass epoxy printed circuit boards best for durability and permanence.
  10. Load relays are D.P. D.T. with latching feature for maximum application versatility.
  11. Electronics are designed to operate on 50/60 Hz, 110 volt current with 10% over or under voltage. Special units for other voltages are available.
  12. Switch set pointers show switch settings at all times.
  13. Spring loaded friction clutch prevents operator damage of set point mechanism.

 

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