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Differential Pressure Gauges and Switches for every need. Mid-West Instrument has been serving a variety of industries (Power, Chemical, Petro-Chemical, HVAC, Water, Filtration) for over 45 years. Over 500,000 Piston Type units have been produced bearing the Mid-West name or private branded for our OEM customers!Mid-West's forte is flexibility and quick response. Standard configurations can be customized and modified to suit a customer's need for easy installation or retrofit.
Differential Pressure is sensed by the movement of a precisely ground floating piston/magnet in a precision bore against a calibrated spring. Any variation in pressure on either side of the piston/magnet will cause the magnet to move proportionally to the change in differential pressure. A rotary pointer magnet located close to the internal magnet, but outside the pressure housing, follows the movement of the piston magnet and indicates differential pressure on the dial.
Piston-Type Differential Pressure Gauges are available with one or two hermetically sealed reed switches. The switches are adjustable within a defined percentage of the full scale range of the gauge and are available in SPDT and SPST, normally open or normally closed configurations for various load/power ratings. The switches can be set to activate or deactivate on rising or falling pressure. Switches are "CE" marked per the EU low voltage directive.
The model 120 can be configured for use in hazardous locations. All hazardous location switches are both CSA and UL listed. The CSA & UL listings are for the entire assembly and not just the enclosure.


  • Differential Pressure Range 0-5 PSID to 0-110 PSID (0-0.35 to 0-7.0 bar)
  • Available in a Variety of Equivalent Ranges and Scales
  • Accuracy ±2%
  • Operating Temperature -40 °F to +200 °F (-40 °C to +93 °C)
  • Dial Size 2-1/2” Round (Standard), 3-1/2” Round (Optional), 4-1/2” Round (Optional)
  • Working Pressures up to 6000 PSIG
  • Material of Construction of Body-Aluminum, 316/316L Stainless Steel, Aluminum Bronze and Monel
  • Materials of Construction of Internals-316 Stainless Steel (Standard) and Monel
  • Switch Options
    • SPDT 3W, 125 VAC/VDC, 0.25 amps, CE
    • SPDT 60W, 240 VAC/VDC, 1.0 amps, CE
    • SPST 60W, 240 VAC/VDC, 3.0 amps, CE
  • Electrical Enclosures Weather-Resistant, NEMA 4X or NEMA 7
  • CE Marked in Accordance with Low Voltage Directive
  • Hazardous Locations
    • Div I
    • Div II

Product Features/Benefits:

  • DP Ranges from 0-5 PSID to 0-110 PSID
  • Piston Sensing Element
  • Working Pressures up to 6000 PSIG (400 bar)
  • Over-Range Protection, High over Low and Low over High
  • Gauge Housings available in Aluminum, Brass, 316/316L Stainless Steel, Aluminum Bronze and Monel
  • Wide Range of Elastomers
  • Simple Rugged Designs
  • Glass Reinforced Thermoplastic Gauge Front is Standard
  • Weather Resistant and Corrosion Resistant Gauge Front
  • Shatter Resistant Lens
  • 5 Year Warranty

Special Features:

  • Over-Range Protection Full to Maximum Working
  • Panel Mounting Standard
  • Pipe Mounting Kit Optional – 2” U-Bolt
  • Wall Mounting Optional – Rear Mount
  • NACE Compliance Optional
  • Seismic Compliance Contact Factory


N/A ±2%

Minimum Differential Pressure Range

N/A 0-5 PSID (0-0.35 bar)

Maximum Differential Pressure Range

N/A 0-110 PSID (0-7 bar)

Maximum Line Pressure PSIG (Bar)

N/A 6000 (400)

Optional Switches

N/A 1 or 2