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Dwyer Instruments A3300-0


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.

Order #: A3300-0

Mfg Part #: A3300-0

$327.00 USD

$317.19 USD


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Overview :

Product Highlights

  • 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)
  • Scale No. 3401 Square Root Specify Range
  • Scale No. 3402 Blank Scale Specify Range
  • Range .25-0-.25" w.c.

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.