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MURPHYGAGES) AND SWICHGAGES' Modeled after the time-and-work-tested, steel case SWICHGAGE , the A20 series offers the same accuracy and durable dependability as the original instruments, also options for ungrounded systems and corrosive environments. These SWICHGAGES , have the front face, adjustable and visible limit contacts that act as switches upon contact with the gauge pointer: wiring is easily completed on the integral, molded terminal block; Environmentally Sealed models do not require oil seal; micro-switches can be added for alarms or to provide a snap-action SPDT SWICHGAGEs Applications: For situations that require accurate gauging of critical pressures that cannot be constantly watched by personnel, the A20 pressure series monitors and can alarm and/or shut-down equipment: on Energy, Agriculture, Industrial, Construction, or Marine installations. STANDARD SPECIFICATIONS : (See also OPTIONS LIST) Dial: 2" (50.8 mm), white on black, psi & kPa Case: 2-3/64" (50.99 mm). black, Lexan' 500/glass filled. Mounting Hole: 2-1/16" (52.4 mm) Mounting Panel Thickness: 1/8" (3.2 mm) max. Mounting Bracket: included Bezel: Polished SS: non-glare black optional Gauge Connection: 1/8-27 NPTM Sensing Element: Diaphragm of beryllium copper Gauge Accuracy: 2%, In the Operating Range (mid 1/3 of scale) Over Pressure: Dial scales 0-15 psi (0-103 kPa) thru 0-200 psi (0-1.38 MPa) withstand up to twice scale; 0-300 psi (0-2.07 MPa) scale. to 500 psi (3.45 MPa) max. SWICHGAGE' Contacts: SPST: pointer and limit contact: N.C. when the low limit is met N.O. when pointer operates above limit Contact Area: pointer is nickel silver: limit contact is silver: current carrying areas are gold flashed. Contacts have patented self-cleaning motion to ensure electrical continuity. Contact Rating: 2 A @ 30 VAC/DC Limit Contact Adjustment: 40% of scale by Allen wrench Wiring Connections: molded terminal block. 4-40 screws Shipping Weight: 8 ozs. (23 kg) Bulletin A20P-7973 Revised 12-30-81 Catalog Section 05 Class (R) A20 Pressure SWICHGAGES Accurate, Visible Gauging & Integral, Adjustable Limit Contacts in one instrument. Polycarbonate/Glass case for corrosive atmospheres and ungrounded electrical systems Case can be Environmentally Sealed Also available as a MURPHYGAGE or with a micro-switch for Alarm Before Shut-down MODELS in the A20 Series of Pressure Instruments: MODEL DESCRIPTION STANDARD A20-PG MURPHYGAGE A20-P std. SWICHGAGE A20-PV HL pressure/vacuum. Hi & Lo with OPTIONS A20-PG ES MURPHYGAGE . Environmental Seal A20-P ES SWICHGAGE , Environmental Seal A20-P HL High & Low contacts A20-PK Knob adj. (1 A @ 125 VAC) A20-PK ES K model, Environmental Seal A20-PK HL K model, High & Low contacts A20-P ABS Alarm Before Shut-down A20- EO SPDT Snap-Action SWICHGAGE' OPTIONS LIST: Gauge Only: Order a MURPHYGAGE Environmentally Sealed: An internal silicone lung compensates for ambient temperature changes, silicone O- rings seal the case. For corrosive atmospheres order models with the "ES" designator. (More Info. on Bul. PA25- 7972) High & Low Contacts: For applications where both high and low pressures are critical, order models with the "HL" designator. Acts as SPDT switch see wiring diagram. K Models: Nylon knob adjustment on front contact models allows SWICHGAGE contact rating. 2 A @ 30 VAC/DC or 1 A @ 125 VAC. Alarm Before Shut-down: std. SWICHGAGE includes a micro switch, preset at the factory to switch for alarm before the front low contact Is made: see Contact Setting Chart, wiring diagram, and description on this bulletin. Snap-Action SWICHGAGE: A20-EO has an internal SPDT micro switch only. for three wire control: can be wired to make or break a circuit. See description., switch set point and wiring diagram on this bulletin

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HOW TO ORDER: Select the A20 pressure model that suits your needs by determining: (1)MURPHYGAGEâ or SWICHGAGEâ (2) Low (std.) or Low & High (HL) contacts (3) or a 3 wire snap-action switch (EO) (4) std. or Environmentally Sealed (ES) (5) type of adjustment: std. (Allen wrench) or Knob (K) (6) Alarm Before Shut-down (7) Operating Range (will fit in mid 1/3 of dial scale) Basic Models A20-PG A20-PG ES A20-PK A20-P ABS A20-P A20-P ES A20-PK ES A20-EO A20-PVHL A20-P HL A20-PK HL Add to the basic model number the psi high point of the dial scale you need: if operating range is 50 psi (345 kPa) to 110 psi (758 kPa), Dial Scale is 0-150 psi (0-1.03 MPa). EXAMPLE: You want a std. SWICHGAGEâ with Knob adj., environmentally sealed. and a dial scale of 0-150 psi: order model A20-PK 150 ES. If you need a snap-action SWICHGAGEâ dial range 0-100 psi, but do not want factory switch Set Point of 15 psi: you want it set at 27 psi: order model A20-EO 100 w/27 psi Set Point. A20-EO: Snap-Action Pressure SWICHGAGEâ The A20- EO models include a standard A series MURPHYGAGE' and an internal, SPDT, snap-action micro switch. The micro switch is adjustable, but field adjustment is not recommended; standard factory settings are listed on the Contact & Micro Switch Set Point Chart, other set points must be specified when ordering. The switch is Set (Wiring Diagram) by falling pressure; the Reset point will be approximately 100/o of scale above that Set point. (10% differential is inherent in the physical movement of the SPDT micro switch.) By knowing the low side setting. this 3 wire SWICHGAGEâ can be used to make or break a circuit. For example: you have a 100 psi A20-EO, factory set at 15 psi: the switch will snap open at + 10% of scale, about 25 psi: this A20-EO 100 could be used to light a lamp (Set/NC) during engine start-up, then put out the lamp as operating pressure rises above 25 psi. The micro switch is rated 4 A @ 125 VAC and 3 A @ 30 VDC Inductive. When specifying Set Point, keep it in the lower 50% of scale. The Pressure Ranges* listed below are available for A20 series MURPHYGAGES and SWICHGAGES see Contact & Micro Switch Set Point Chart for standard factory settings. DUAL PRESSURE SCALES Add to model # psi kPa/MPa dial scale key 0-15psi 0-103 kPa 15 0-30 psi 0-207 kPa 30 0-50 psi 0-345 kPa 50 0-75 psi 0-517 kPa 75 0-100 psi 0-689 kPa 100** 0-150 psi 0-1.03 MPa 150 0-200 psi 0-1.38 MPa 200 0-300 psi 0-2.07 MPa 300 *A20-PVHL has ONE RANGE ONLY: 5 psi to 20" Hg vacuum. **Standard Dial Scale CONTACT & MICRO SWITCH SET POINT CHART:^a Pressure Range Std. models contract HL models contacts low high ABS models^b Cont./Switch Low High EO models^b SPDT switch Low 0-15 3 3 12 3 6 3 0-30 7 7 24 5 8 5 0-50 10 10 40 8 11 8 0-75 15 15 60 10 13 10 0-100 20 20 80 15 18 15 0-150 30 30 120 20 23 20 0-200 50 50 150 50 53 50 0-300 75 75 225 75 78 75 ^aChart is in psi, and settings are manufacturer recommended. Standard SWICHGAGEâ can be adjusted in the field. ^bABS and EO micro switch settings are not easily adjusted in the field: switches are set at Std. unless Specified when ordering. A20-P ABS: SWICHGAGE' with Alarm Before Shut-down The A20-P ABS has a standard front adjustable low contact for equipment shut-down, and an internal micro switch for alarm before shut-down (see wiring diagram). The front contact is wired to the NC terminal of the SWICHGAGEâ and is set at the std. low pressure shut-down point. The internal switch has one side of a SPDT switch set to contact just before shut-down pressure. The NO terminal connects the micro switch to alarms. Both the adjustable, front contact and the micro switch are preset at the factory: if settings other than standard are necessary, specify your Set Points when ordering. STANDARD WIRING DIAGRAMS: A20 Pressure Series. The circuits are shown with pressure in the operating range. STANDARD WIRING DIAGRAMS: A20 pressure series. The circuits are shown with pressure in the operating range.

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