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Pressure & Vacuum Measurement
Solutions

221Baratron® General Purpose Differential 		
Pressure Transducer
The 221 Baratron® General Purpose Differential Transducer offers a reliable, accurate,
inexpensive solution to measuring low differential pressures.
Operating on the variable capacitance technique, the 221 all-metal sensor contains atensioned metal diaphragm, one side of which is exposed to the gas whose pressure is tobe measured (Px side). The other side (reference, or Pr, side) is adjacent to an electrodeassembly which is terminated in another like port. The diaphragm deflects with changing
differential pressure, causing a capacitance change between the diaphragm and theadjacent electrode assembly. The capacitance change with pressure generates an AC
voltage which is amplified, demodulated, and converted into a high level DC voltage output,
linear with pressure, and calibrated against a pressure standard.
The electronics of the 221 are housed remotely from the sensor, allowing it to be baked at200°C (with interconnecting cable removed). An MKS or user-supplied power supply/readout
is required to operate the 221.

Features & Benefits• All-metal sensor eliminates handlingproblems associated with glass, mercury, 		and liquid gauges• Useable resolution of 1 part in 10,000— minimizes the number of transducers 				 required to cover a wide range of 				 pressures• Remote electronics allow sensor tooperate at temperatures up to 150°C 		(bakeable to 200°C with cable removed)• Sensor is capable of handling any
corrosive gases compatible with Inconel 		on high pressure side and Inconel, 			Ceramic, Palladium, Glass and Stainless 			Steel on reference sideSpecifications andOrdering Information
Full Scale Ranges
10, 100, 1000, 5000, 10000, 15000, 20000, 25000 mmHg
Resolution
0.01% of F.S.
Accuracy
0.5% of Rdg. (± temperature coefficients)
Temperature Coefficients											
Zero0.02% of F.S./°C									
Span0.04% of Rdg./°C
Ambient Operating Temperature												Sensor
0° to 150°C (bakeable to 200°C with cable removed)					Preamp0° to 50°C
Maximum Overpressure
120% of F.S. or 20 psi (140 kPa), whichever is greater(For Full Scale ranges less than 1000 mmHg, the following restrictions apply: if high pressure		is on the Px side of the sensor, the maximum differential overpressure allowable is 120% of		F.S. or 20 psi, whichever is greater; if high pressure is on the Pr side of the sensor, the 				maximum differential overpressure allowable is 120% of F.S. Consult factory for higher Pr		
overpressure protection.)
Maximum Line Pressure
40 psig (275 kPa)
Materials Exposed to Gases										Px side	Inconel										Pr side	Inconel, Ceramic, Palladium, Stainless Steel, Glass
VolumePx side: 7.9 cc
Pr side: 19.0 cc
Fittings												Standard½” (12.7 mm) tubulation									Optional	Swagelok® 8 VCR® female, NW 16 KF, mini-CF rotatable (High pressure units, 5000 to 25000		
mmHg F.S., supplied with 8 VCR fittings only.)
Power Required±15 VDC @ 35 mA regulated ±2%
Output0 to 10 VDC into > 10K Ω load
Electrical Connector
AMP 14-pin ribbon connectors; MKS Connector Kit, 221B-K1
Ordering Code Example: 221BD00100A
221BD	Code	Configuration
221BD
221BD
221BD
Pressure Range Full Scale
10100
1000
5000
10,00015,00020,00025,00000010			00100			01000			05000			0010010000			15000			20000			25000Fittings½” OD (12.7 mm) diameter tube
A			
Swagelok 8 VCR female
BA	Mini-CF, rotatable	C				NW 16 KF
DDimensional Drawing —Note: Unless otherwise specified, dimensions
are nominal values in inches (mm referenced).

221 - 1/18
© 2004-2018 MKS Instruments, Inc.
All rights reserved.

MKS Instruments, Inc.
Global Headquarters

MKS Instruments, Inc.		
Pressure & Vacuum Measurement Solutions

2 Tech Drive, Suite 201
Andover, MA 01810

Six Shattuck Road
Andover, MA 01810

Tel: 978.645.5500
Tel:  800.227.8766 (in U.S.A.)
Web: www.mksinst.com

Tel: 978.975.2350

Some Baratron® capacitance manometer products may not be exported to many end user countries without both US and local
government export licenses under ECCN 2B230.
Specifications are subject to change without notice. mksinst™ is a trademark and Baratron® is a registered trademark of MKS
Instruments, Inc., Andover, MA. Swagelok® and VCR® are registered trademarks of Swagelok Marketing Co., Solon, OH.
AMP™ is a trademark of AMP Incorporated, Harrisburg, PA.