美国摩菲MURPHY 20系列（2英寸/51毫米刻度盘）和25系列（2 1/2英寸/64毫米刻度盘）开关仪表是隔膜驱动的真空指示仪表，带有内置的电气开关。这些开关用于跳闸报警和/或停机装置。MURPHY 20 Series (2 inch/51 mm dial) and the 25 Series (2 1/2 inch/64 mm dial) Swichgage instruments are diaphragm-actuated, vacuum-indicating gages with built-in electrical switches. These switches are used for tripping alarms and/or shutdown devices.
MURPHY 20V / 25V系列真空SWICHGAGE开关表
- 2英寸和2.5英寸（51mm和64mm）
- 0-20或0-30英寸汞柱（0-68 or 0-102kPa）(0-68 or 0-102bar)
- 表面可调节高低限位触点
The 20 and 25 series gage mechanism is enclosed in a steel case coated to resist corrosion.
A-Series gages have a polycarbonate case and are sealed from the environment. All gages feature a polycarbonate, break-resistant lens and a polished, stainless steel bezel to help protect these rugged, built-to-last instruments.
The gage pointer acts as a pressure indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contacts have a self-cleaning motion to ensure electrical continuity.
Gage-only models, without contacts (Murphygage? instruments) are also available.
A pulsation dampener (PD2160) is included with each Swichgage to help eliminate pointer flutter. When monitoring intake manifold vacuum, the PD2160 is mounted in the manifold. The PD2160 has a 1/8-27 NPT connection.
Commonly used to measure loading of spark-ignition engines through intake manifold vacuum, the gages also can serve as overspeed protection from sudden loss of load on these engines. Use anywhere the vacuum source is compatible with port materials.
Dial : White on black, dual scale; U.S.A. standard scale is Inches of Hg/kPa
Case (mounting clamp included) :
20 and 25 Series: Plated steel
A20 and A25 Series: Polycarbonate/glass filled
Bezel : Polished stainless steel, standard; others are available (see How to Order)
Lens : Polycarbonate, high-impact
Process Connection : 1/8-27 NPTM brass
Sensing Element : Beryllium copper diaphragm
Gage Accuracy : ±2% of scale in operating range (mid 1/3 of scale)
Adjustable Limit Contacts :
2-SPST contacts; pilot- duty only, 2 A @ 30 VAC/DC. Contacts are gold flashed silver.
Limit Contact Adjustment: by a 1/16 in. hex wrench
Limit Contact Wire Leads (20 and 25 Series): 18 AWG (1.0 mm2) x 12 in. (305 mm)
Limit Contact Terminals: A20 Series number 4 screw terminals; A25 Series number 6 screw terminals
Unit Weight :
20 Series: 8 oz. (0.23 kg)
25 Series: 11 oz. (0.31 kg)
A20 Series: 6 oz. (0.17 kg)
A25 Series: 10 oz. (0.28 kg)
Unit Dimensions :
20 and A20 Series: 3 x 3 x 3 in. (76 x 76 x 76 mm)
25 and A25 Series: 4-3/4 x 4-3/4 x 2-3/4 in. (121 x 121 x 70 mm)
