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Differential Pressure Gauges & Switches

Mid-West Instrument – Differential Pressure Gauges & Switches

Mid-West Instrument, located in Sterling Heights, MI is one of the leading designers and manufacturers of differential pressure (DP) gauges and switches in the U.S. The firm’s experienced engineers and technicians utilize the latest equipment for engineering, manufacturing and testing the firm’s gauge and switch products.

CMC Technologies is the sole and exclusive distributor (since 1999) for Mid-West Instrument in Australia and New Guinea. We hold stocks of DP Gauges and back flow test kits in Sydney and are the only Factory Authorised Calibration and Service centre in South East Asia.

Differential pressure is sensed either by the movement of an elastomer diaphragm or a precision ground piston in a precision controlled bore. The change in position of these sensing elements in response to a change in differential pressure moves an internal magnet. The movement of this magnet causes the closure (or opening) of the contacts of a hermetically sealed reed switch.

– Mid-West Instrument website

In Piston Type DP gauges, 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.

In Diaphragm Type DP gauges, differential pressure is sensed by the movement of an elastomer diaphragm against a precision calibrated range spring. The change in position of the diaphragm in response to the change in Differential Pressure moves an internal magnet. This magnet, in turn, causes a rotary magnet external to the gauge body to rotate. This rotary magnet has a pointer attached which indicates the differential pressure on the dial.

The Model 109 is powered by a test quality Bourdon Tube Assembly. The assembly is encapsulated in a high pressure chamber that is fitted with a pressure connection to the inside of the Bourdon Tube and a second connection to the pressure chamber. The Model 109 indicates the difference between the pressure applied inside the Bourdon Tube and the pressure inside the chamber.

The major components of the Model 105/106 are a two-piece body, bellows sensing element and over-pressure assembly, a torque tube assembly, a range spring and the gauge front assembly.

The body halves provide the pressure containment function. They also clamp the sensing element and over-pressure assembly between the halves, isolating the high side and low side pressures of the system. The high side body half also provides a mount for the torque tube assembly and the gauge front assembly.

>> Model 150 Pulsation Dampener
>> Model 200 Pressure Limiting Valve (“Gauge Minder”)
>> Manifold Valves (Manifolds)