Differential Pressure Unit

The Meriam Model 1020 Differential Pressure Unit is a proven and reliable sensing element. Available in ranges from as low as 0-30” H2O to 0-500 PSI. It is especially adaptable where size and weight are critical factors. The light weight and compact differential pressure unit incorporates a rupture-proof and leak-proof bellows plus other construction features that make it second to none. This unit is suitable for activating indicators, recorders, transmitters, switches and controllers and is available as a separate assembly for that purpose.

The basic D/P unit consists of a high and a low pressure bellows, both liquid filled and connected to a center plate. The bellows are enclosed in the high and low pressure end housings which in turn  are bolted to the center plate. When differential pressures are applied to the high and low pressure connections, the high pressure bellows contracts forcing the fill fluid through the center plate into the low pressure bellows causing it to expand. The resulting linear motion of the low pressure bellows is converted to a 6° rotary motion of the output shaft through a temperature compensated linkage. Over-range protection is provided by two opposed valves located on this linkage allowing the unit to withstand over-ranging up to the full static pressure rating of the housing without damage. The interior of the bellows and center plate are completely filled with a clean, non-corrosive, low freezing point liquid. This output shaft is part of a low friction, “0” ring sealed shaft and bearing assembly which carries the rotary motion to the external area of the bellows unit and into the instrument case.

In the Meriam bellows unit all of the fill fluid must pass through the Meriam Pulsation Dampening valve in the center plate. This valve is field adjustable so that the desired dampening effect can be obtained. Because of this Meriam design, other types of external dampening devices are not required on services involving measurement of fluctuating differential pressures. The Meriam bellows D/P unit incorporates a special design which completely isolates the process fluid from the center plate.

Model 1020 Features
• Range variations
• Material variations, housing, bellows and center plate
• Rugged construction for long life
• 6° output shaft rotation
• Temperature compensation for varying ambient conditions
• Integral field adjustable pulsation dampening
• Low friction “O” ring sealed output shaft
• Over-range protection - high and low pressure
• Seamless leak-free bellows
• Process isolation rings

Performance Specifications

Independent
0 to 30” W.C. range ±1.50% FS

Linearity
0 to 50” W.C. thru 0 to 500 PSID range ±0.75% FS

Temperature Limits
-60°F to +200°F

Full Scale Displacement
0 to 30” thru 0 to 130” W.C. range .19 Cu. In.
0 to 130” W.C. thru 0 to 60 PSID range .12 Cu. In.
0 to 75 PSID thru 0 to 500 PSID range .06 Cu. In.



Ordering Information
To order Meriam’s Model 1020 Differential Pressure Unit, custom-made to your specifications, please contact your Meriam sales representatives with the following information:
• Model Number
• Housing Material
• Safe Working Pressure
• Bellows Material
• Differential Range