Photohelic Pressure Switch-Gage with Integral Transmitter
Indicating Gage, Low and High Limit Control, 4-20 mA Transmitter
The Dwyer Series 3000 SGT Photohelic Pressure Switch Gage Transmitter combines several critical control functions into 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 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 set point 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 set point 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.
PHYSICAL DATA – GAGE SPECIFICATIONS
- Service: Air and non-combustible, compatible gases.
- Wetted Materials: Consult factory.
- Accuracy: See model chart on “Ordering” page.
- Pressure Limits: See model chart on “Ordering” page.
- Temperature Limits: 20 to 120°F (-6.67 to 48.9°C).
- Process Connections: 1/8″ female NPT.
- Size: 4″ (101.6 mm) dial face, 5″ (127 mm) O.D. x 8-1/4″ (209.55 mm).
- Weight: 3 lb 14.5 oz (1.77 kg).
PHYSICAL DATA – SWITCH SPECIFICATIONS
- Switch Type: Each set point has 2 Form C relays (DPDT).
- Repeatability: ±1% of full scale.
- Electrical Rating: 10A @ 24 VDC or 120 VAC, 6A @ 240 VAC.
- Electrical Connections: Screw terminals.
- Power Requirements: 120 VAC, ±10%.
- Mounting Orientation: Diaphragm in vertical position. Consult factory for other position orientations.
- Set Point Adjustment: Adjustable knobs on face.
PHYSICAL DATA – TRANSMITTER SPECIFICATIONS
- Accuracy: See model chart on “Ordering” page.
- Temperature Limits: 20 to 120°F (-6.67 to 48.9°C).
- Pressure Limits: See model chart on “Ordering” page.
- Thermal Effects: ±0.025% F.S./°F (0.045% F.S./°C).
- Power Requirements: 10.0 to 35 VDC (2-wire).
- Output Signal: 4-20 mA DC.
- Zero & Span Adjustments: Multi-turn potentiometers, internally accessible.
- Response Time: 250 mSec.
- Loop Resistance: 0-1250 ohms.
- Current Consumption: 38 mA DC, maximum.
- Electrical Connections: Terminal block.
- Warm-up Time: 10 minutes.
OPTIONS AND ACCESSORIES
Tamper-Proof Knobs: Require special spanner-type key (included) to adjust set points. Add suffix -TAMP
A-700 Power Supply: AC input: 100/120/220/230-240 VAC ±10%, 47-63Hz. DC output: 24-28 VDC regulated
AVAILABLE MODELS
| MODEL | RANGE | MEASUREMENT | MAX PRESSURE |
|---|---|---|---|
| 3000SGT-0 | 0-0.5" w.c. | w.c. | 25 psi |
| 3001SGT | 0-1.0" w.c. | w.c. | 25 psi |
| 3002SGT | 0-2.0" w.c. | w.c. | 5 psi |
| 3003SGT | 0-3.0" w.c. | w.c. | 5 psi |
| 3006SGT | 0-6.0" w.c. | w.c. | 5 psi |
| 3010SGT | 0-10.0" w.c. | w.c. | 5 psi |
| 3020SGT | 0-20.0" w.c. | w.c. | 10 psi |
| 3030SGT | 0-30.0" w.c. | w.c. | 10 psi |
| 3000SGT-250PA | 0-250 Pa | Pa | 25 psi |
| 3000SGT-500PA | 0-500 Pa | Pa | 5 psi |
| 3000SGT-1.5KPA | 0-1.5 kPa | kPa | 5 psi |
SUGGESTED SPECIFICATIONS
Differential pressure switches shall incorporated gages and switch setpoint indicators for continuous indication of applied pressure and switch settings. An integral 4-20 mA pressure transmitter shall be included, calibrated for the range of the pressure gage. Separate zero and span potentiometers shall be provided. Units shall be diaphragm operated with switching accomplished by phototransistor controlled DPDT relays. Setpoint adjustment shall be controlled by knobs on front of unit. Switch/Gage/Transmitter shall be Dwyer Instruments, Inc., Photohelic® Catalog Number.___ reading to ___ (in. w.c.)(Pa)(kPa) in ___ minor divisions.