Compare Description Drawings, CAD & Specs Full Scale Range Analog Output Fitting Type Availability Price
228a baratron 0.2-1000 torr differential capacitance manometer with 2 trip points
10 Torr 0 - 5 VDC 0.25 in. OD tube
228a baratron 0.2-1000 torr differential capacitance manometer with 2 trip points
100 kPa 0 - 5 VDC 0.1875 in. OD tube
228a baratron 0.2-1000 torr differential capacitance manometer with 2 trip points
200 mbar 0 - 10 VDC ISO-KF and 0.25 in. OD tube
228a baratron 0.2-1000 torr differential capacitance manometer with 2 trip points
50 in. H2O 0 - 1 VDC 4 VCR male

Configuration Options

228a baratron 0.2-1000 torr differential capacitance manometer with 2 trip points 228A Differential Capacitance Manometer, 2 Trip Points, 228A Series


  • Type
    Pressure Transducer
  • Sensor Type
    Capacitance Manometer
  • Measurement Type
  • Full Scale Pressure Ranges
    0.2, 1, 2, 5, 10, 20, 50, 100, 200, and 1000 Torr and equivalents in kPa, mbar, inches H2O, and cm H2O
  • Analog Output
    0-1 VDC, 0-5 VDC, or 0-10 VDC > 10 kΩ load
  • Fitting Type
    Standard: 1/4 inch OD (6.4 mm) tubes
    Optional: Various
  • Electrical Connector
    15-pin high-density D-subminiature
  • Resolution
    0.01% of Full Scale
  • Accuracy
    0.50% of Full Scale unidirectional or bidirectional standard
    0.30% of Full Scale unidirectional or bidirectional
    0.30% of Reading (unidirectional only) optional
  • Zero Temperature Coefficient
    0.1% Full Scale/°C for standard accuracy specification
  • Span Temperature Coefficient
    0.04% of Reading/°C
  • Sensor Internal Volume
    Measurement Side (Px):1.4 cm
    Reference Side (Pr):9.0 cm
    (when equipped with standard 1/4-inch (6.4 mm) O.D. inlet and reference tubes)
  • Operating Temperature Range
    0° to 50°C
  • Maximum Overpressure
    Measurement Side (Px):120% of Full Scale or 20 psi (140 kPa), whichever is higher
    Reference Side (Pr):120% of Full Scale
  • Maximum Line Pressure
    40 psig (275 kPa)
  • Materials Exposed to Process Gases
    Measurement Side (Px):Inconel
    Reference Side (Pr):Inconel, ceramic, palladium, stainless steel, glass
  • Trip Points
    Two process pressure trip points, independently adjustable from -100% to +100% of Full Scale
  • Trip Relays
    DPDT contacts rated at 1.0 amps at 30 VDC or 0.3 amps at 120 VAC
  • Power Requirements
    ±15VDC (±5%) or +16 to +30VDC @ 75 mA, ripple less than 20 mV
  • Compliance
    CE, SEMI S2


Differential Pressure Measurement

Differential capacitance manometers can be connected to any pressure or vacuum source for use as the reference pressure. These manometers read the difference in pressure between the inlet tube and the reference cavity at the backside of the electrode. Differential pressure transducers can be used to measure either the true differential pressure or vacuum between two locations, or the reference side of the product can be left open to provide a true reference to local atmospheric pressure. Applications include air and gas flow measurements for filters and analytical systems, downstream pressure control in thin film processing systems, and automated leak testing systems.

Inconel® Nickel Alloy Construction

The patented capacitance sensor is built entirely from Inconel® nickel alloys on its measurement side, which offers superior corrosion resistance over long periods of time. Inconel® construction also offers high overpressure tolerances that reduce errors due to line pressure spikes, and high burst pressure ratings that contribute to overall system safety.

Three Analog Outputs

Three (3) different analog output signals (0-1 VDC, 0-5 VDC, and 0-10 VDC) are included for use in nearly any control or data acquisition system.

Twelve Different Fitting Types

These Baratron® differential capacitance manometers can be equipped with any of twelve (12) different fittings on either the measurement or reference sides, including common industrial and semiconductor-industry standards like VCR®, NW-KF, VCO®, and NPT.

Two Independently Adjustable Trip Relays

Two (2) independently-adjustable trip relays are included for control of external equipment and components based on a pressure trip point.  The trip points are adjustable from -100% to +100% of the full-scale measurement range. The DPDT relay contacts are rated at 1.0 amp at 30 VDC or 0.3 amp at 120 VAC.

Baratron® Capacitance Manometer Technology

Capacitance manometers are electro-mechanical gauges that can measure both pressure and vacuum. The capacitance gauge translates a pressure-modulated movement in a thin diaphragm into an electrical signal proportional to the pressure. The pressure sensor is the thin diaphragm that is exposed to the pressure or vacuum being measured via the inlet tube. An electrode is mounted in the reference cavity behind the diaphragm. Pressure differences between the process and the reference cavity deflect the diaphragm slightly, changing the distance between it and the electrode. Variations in this distance produce variations in the capacitance between the diaphragm and the electrode creating an electrical signal that is proportional to the pressure change. Since differences in the capacitance signal are produced by physical changes within the manometer and not by changes in the gas properties, pressure measurements by the capacitance manometer are independent of the composition of the gas being measured.

Capacitance manometer sensor schematic showing the internal components

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