The 228A Differential Baratron® is a general-purpose differential capacitance manometer is available in full-scale measurement ranges from 0.2 to 1000 Torr, two trip relays, and can be configured with a wide variety of fittings, input/output signals, and electrical connectors. It is mounted in a rugged industrial-grade housing that minimizes external RF/EM interference on the electronics.
- Differential pressure measurement from 1000 to 0.2 Torr
- Two independently-adjustable trip relays
- Three different analog output signals for unidirectional or bidirectional calibrations
- Gas composition independent pressure measurement
- Fully-welded Inconel® sensor resists corrosion See All Features
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Configuration Options
The following options are available for the 228A Baratron® Differential Capacitance Manometer.
Ordering Code Example: 228AXXXYYZZQSSTVRR
| Configuration Option | Option Code |
|---|---|
| 228A Baratron Differential Capacitance Manometer | 226B |
Pressure Range |
|
| 0.02 (kPA only) | U2 |
| 0.1 (kPA & inH2O only) | .1 |
| 0.2 (not available inH2O) | .2 |
| 0.5 (kPA & inH2O only) | .5 |
| 1 | 01 |
| 2 | 02 |
| 5 | 05 |
| 10 | 11 |
| 20 | 21 |
| 50 (not available for kPA) | 51 |
| 100 | 12 |
| 200 (not available for kPA & inH2O) | 22 |
| 500 (inH2O only) | 52 |
| 1000 (not available for kPA & inH2O) | 13 |
Engineering Units |
|
| Torr/mmHg | T |
| mbar | M |
| kPa | K |
| inH2O | W |
| cmH2O | R |
Reference Side Fitting (compatible with) |
|
| 0.25 in. OD tube | BB |
| 0.1875 in. OD tube | BG |
| 4 male VCR | CB |
| 4 female VCR | CD |
| 4 male VCO | DC |
| 4 female VCO | DD |
| 0.25 in. female NPT | FA |
| 0.25 in. male NPT | FB |
| 0.125 in. male NPT | FE |
| 0.125 in. female NPT | FF |
| NW16 KF | GA |
| 1.33 in. OD Conflat | HA |
Measurement Side Fitting (compatible with) |
|
| 0.25 in. OD tube | BB |
| 0.1875 in. OD tube | BG |
| 4 male VCR | CB |
| 4 female VCR | CD |
| 4 male VCO | DC |
| 4 female VCO | DD |
| 0.25 in. female NPT | FA |
| 0.25 in. male NPT | FB |
| 0.125 in. male NPT | FE |
| 0.125 in. female NPT | FF |
| NW16 KF | GA |
| 1.33 in. OD Conflat | HA |
Accuracy |
|
| 0.50% Full Scale (standard) | F |
| 0.30% Full Scale | K |
| 0.30% Reading (unidirectional calibrations only) | S |
Input/Output & Calibration |
|
| ±15 VDC input/0-1 VDC bidirectional output | B1 |
| ±15 VDC input/0-10 VDC bidirectional output | B2 |
| ±15 VDC input/0-5 VDC bidirectional output | B3 |
| +24-32 VDC excitation/4-20 mA bidirectional output | B4 |
| +24 VDC input/0-1 VDC bidirectional output | B5 |
| +24 VDC input/0-5 VDC bidirectional output | B7 |
| ±15 VDC input/0-1 VDC unidirectional output | U1 |
| ±15 VDC input/0-10 VDC unidirectional output | U2 |
| ±15 VDC input/0-5 VDC unidirectional output | U3 |
| +24-32 VDC excitation/4-20 mA unidirectional output | U4 |
| +24 VDC input/0-1 VDC unidirectional output | U5 |
| +24 VDC input/0-5 VDC unidirectional output | U7 |
Electrical Connector |
|
| 9-pin D-subminiature (standard) | A |
| Terminal block adaptor, 5-post | T |
| Flying lead adapter, 10 ft (3 m) length | L |
Mounting |
|
| No bracket | 0 |
| Mounting bracket, standard | 1 |
| Mounting bracket, slotted | 2 |
Trip Relay Settings |
|
| Trip A above 50% Full Scale, Trip B above 50% Full Scale* (default setting) | AA |
| Trip A above 50% Full Scale, Trip B below 50% Full Scale* | AB |
| Trip A below 50% Full Scale, Trip B below 50% Full Scale* | BB |
| Trip A below 50% Full Scale, Trip B above 50% Full Scale* | BA |
| *Contact factory for alternate trip relay settings | |
Specifications
- TypePressure Transducer
- Sensor TypeCapacitance Manometer
- Measurement TypeDifferential
- Full Scale Pressure Ranges0.2, 1, 2, 5, 10, 20, 50, 100, 200, and 1000 Torr and equivalents in kPa, mbar, inches H2O, and cm H2O
- Analog Output0-1 VDC, 0-5 VDC, or 0-10 VDC > 10 kΩ load
- Fitting TypeStandard: 1/4 inch OD (6.4 mm) tubes
Optional: Various - Electrical Connector15-pin high-density D-subminiature
- Resolution0.01% of Full Scale
- Accuracy0.50% of Full Scale unidirectional or bidirectional standard
0.30% of Full Scale unidirectional or bidirectional
0.30% of Reading (unidirectional only) optional - Zero Temperature Coefficient0.1% Full Scale/°C for standard accuracy specification
- Span Temperature Coefficient0.04% of Reading/°C
- Sensor Internal VolumeMeasurement 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 Range0° to 50°C
- Maximum OverpressureMeasurement Side (Px):120% of Full Scale or 20 psi (140 kPa), whichever is higher
Reference Side (Pr):120% of Full Scale - Maximum Line Pressure40 psig (275 kPa)
- Materials Exposed to Process GasesMeasurement Side (Px):Inconel
Reference Side (Pr):Inconel, ceramic, palladium, stainless steel, glass - Trip PointsTwo process pressure trip points, independently adjustable from -100% to +100% of Full Scale
- Trip RelaysDPDT 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
- ComplianceCE, SEMI S2
Features
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.
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.
Accessories
Power Supplies and Displays
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Resources
Literature
228A Baratron® Differential Capacitance Manometer Datasheet(239.6 kB, PDF)
Application Notes
Pressure-based Leak Testing(201.7 kB, PDF)
Manuals
MKS 226B & 228A Differential Transducers Manual(609.2 kB, PDF) 228A Differential Capacitance Manometer Pin-outs(24.5 kB, PDF)












