Making the right decision for your differential pressure application? Piston vs Diaphragm |
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Mid-West Piston Type: ± 2% or ± 5% Full Scale Accuracy. They are primarily designed for liquid applications. They exhibit a slight amount of bypass as the fluid crosses from the high to the low pressure port. Because gas molecules are smaller, the crossover is often deemed too great for the application. The 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. Note: Due to precision sizing of piston and body bore, leakage across the piston will not exceed 15 SCFH air at 100 P.S.I.D. at ambient conditions. Contact Mid-West @ 1-800-648-5778 for more information. |
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Mid-West Diaphragm Type: ± 2% Full Scale Accuracy. The high and low-pressure ports are completely isolated from each other. There is no bypass and therefore they are best suited for air or gas along with liquids. They also come in a variety of sizes allowing for very sensitive measurements. The 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 diaphragm prohibits the possibility of fluid leaking into the gage case, while assuring total isolation of the process fluid within the pressure capsule. The diaphragm assures total separation between the high and low pressure signals. Diaphragm-type Differential Pressure Gauges are also available with one or two hermetically sealed reed switches. The switches are adjustable (see table for the adjustment range) within a defined percentage of the full scale range of the gauge and are available in SPDT and SPST, normally open 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. Contact Mid-West @ 1-800-648-5778 for more information. |