The
Series 3000SGT Photohelic® Switch/Gage/Transmitter combines several
critical control functions ito a single, easy-to-install package. This
versatile instrument starts with the universally accepted standard for
reliable low air pressure measurement, the Dwyer Magnehelic® Gage. It
measures positive, negative or differential pressures within ±2% of
full scale accuracy. This time-proven component provides highly legible
analog indication of air or compatible gas pressure on a 4", 80°
scale. Gage operation is completely independent - functions normally
even if power is interrupted to electrical elements of the control.
Next, two DPDT relays are added which serve as Low/High limit controls
(or pressure switches) capable of handling up to 10 amps @ 24 VDC or 120
VAC directly. Individual setpoint deadband is one pointer width - less
than 1% of full scale; just enough to assure positive, chatter-free
operation. Integral holding coils enable user to connect the two so they
work like a single control with variable deadband - ideal for
applications such as clean room and building pressurization, HVAC
systems, automatic air filter or level control and much more. Actuation
points are fully adjustable over the entire pressure range with
convenient from mounted knobs linked to bright red setpoint indicators.
Finally, the Photohelic® SGT includes a separate 4-20 mA, 2-wire
transmitter operating from an external 12.3 - 35 VDC power supply.
Separate adjustments are included for zero and span inside the rear
electronics enclosure. Optional A-700 Power Supply is a perfect
companion rated for AC inputs from 100-240V; DC outputs from 24 - 28V.
The transmitter component is an ideal driver for variable speed blowers
and fans, damper positioners and for continuous data logging on
computerized VAV systems or strip chart recorders. Besides the obvious
cost and space saving advantages of combining all these control
functions in a single unit, think of the additional savings in time and
material with just one set of pneumatic lines to connect instead of
three or four.
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