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Both
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 plastic 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: -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.
Accuracy: ±2% of full scale at 70°F (21 .1°C). 3% on -0 and
4% on -00 models.
Gage Connections: 1/8" NPT(F).
Power Required: 120 VAC, 50/60 Hz
Electrical Rating of Relays: 10 A @ 120 VAC, 6 A @ 240 VAC,
60 Hz res.
Conduit Opening: ¾" conduit.
Finish: Dark gray
Weight: Photohelic, 4 lbs. (1.8 kg). Use with air or compatible
gases only.
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