The Series 3000SGT Photohelic® Switch/Gage/Transmitter
combines several critical control functions into a single, easy-to-install package. This versatile instrument starts with the universally accepted standard forr 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 reliable 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 @ 28 VDC or 120/240 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 front mounted knobs linked to bright red setpoint indicators.
Finally, the Series 3000SGT Photohelic® Switch/Gage includes a separate 4-20 mA, 2-wire transmitter operating from an external 10-35 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.