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Valve Solutions

Complete closed-loop
electronic pressure
controllers with integrated
transducers in single
compact packages

640B/641B
Electronic Pressure Controller
The 640B and 641B Pressure Controllers are self contained, compact, closed-loop
electronic pressure control systems. Each contains a capacitance manometer, normallyclosed proportioning control valve, and closed-loop control electronics. The 640B controls
absolute pressure; the 641 controls gauge pressure, (pressure relative to ambient barometricpressure). Both transducers are Baratron® capacitance manometers, with Full Scalepressure ranges from 100 psi to as low as 10 Torr. Baratron capacitance manometers –well-known for their percent of Reading accuracy, stability, and resolution – provide precise
measurements at lower pressures and over wider dynamic ranges than strain gaugetransducers. Furthermore, Baratron capacitance manometers have no silicone oil fill which
can result in hysteresis and can slow the controller time response.
Electrically similar to a standard MFC, the 640B/641B are powered by ±15 VDC at only 200mA, permitting use with standard power supply/display electronics. The pressure output andinput control signals are linear 0-5 or 0-10 VDC. Two trip points are included in the 640/641,
with LED status indicators, for use as simple on/off process limits.
During final testing at MKS, the 640/641 control loop tuning parameters are preset for
typical installation conditions, but are field adjustable for different conditions and optimum
performance. The Proportional and Integral Term adjustments are simple rotary switches,rather than potentiometers, to enable OEMs, or users with multiple controllers, to preset allunits to the same control loop parameters.

Features & Benefits• Integral Baratron capacitancemanometer provides accuracy,reliability, and wide range• Perform closed-loop electronic pressure
control in-line with compact, 3” MFC-type 		
footprint package• Controller Full Scale ranges as low as
10 Torr for use in low pressure processes• Reduce overall system cost while saving
valuable rack space• Can be used with upstream or
downstream controller applications• Obtain precise, repeatable pressure
control/measurement over wide rangeof pressures with proven Baratron® 		
capacitance manometer technology• Controls absolute or gauge pressure• Elastomer and all-metal sealed versions
available• Two alarm trip points for process limit
control

50

30

2

10.5

100

>585

585

480 355 265 190 135

15895

65

50

–

295

295 240 185 13065

50 258530––

175 175 140 100

20

–

–

15

–

–

–

90

90

70

50

35

25

776

10

–

–

–

–

60

55

40

30

20

517
259

– 115 110

480

95

5170

75

50

40

1551

60

40

30

1034

5

–

–

–

–

–

30

25

20

15

2

–

–

–

–

–

–

10

10

9

103

1

–

–

–

–––

–

6

651.7

inlet Pressure (Torr)

inlet Pressure (psia)

Differential Pressure (psi)>50>2585 2585 1551 776 414 207 103 51.7 25.9

Differential Pressure (Torr)
Figure 1 —Figure 2 —Index Number Table (See Note)

Orifice Selection Graph (See Note)

Valve Orifice

Pressure Range

The flow through any orifice depends on the size of theorifice, the inlet and outlet pressures, and gas density.
To simplify 640/641 orifice selection, use the following
procedure:In the 640 Controller, the Baratron pressure transducer
measures absolute pressure; in the 641 model, itmeasures gauge pressure (pressure relative to ambient
barometric pressure). In both models, Full Scale ranges of
10, 100, or 1000 Torr, or 60 or 100 psi are available. Each640/641 can control pressure from Full Scale to less than
2% of Full Scale. Prudent design suggests choosing thelowest possible Full Scale for the application, taking into
consideration the overpressure to which the sensor may
be exposed (both normal and accidental).

1. On the Index Number Table in Figure 1, choose yourinlet pressure from the column of pressures on the 		left – the pressure that will be applied to the inlet of your640/641. (Note that the values are absolute pressure.)
2. Next, from the row of pressures at the top of that table,
select your differential (delta) pressure – this is the inlet
pressure minus your outlet pressure.
3. Locate the Index Number – where your selected row
and column intersect.
4. If you are using N2, skip to step #6. For other gases,
calculate the Density Correction Factor by the following
formula:Density Correction Factor = N2 Density
Gas Density
5. Multiply this Density Correction Factor times the Index
Number found in step 3, to determine your density-		corrected Index Number.
6. Go to the Orifice Selection Graph (Figure 2) and locate
your Index Number along the bottom axis.
7. Draw a vertical line at your Index Number. This line willintersect with the Maximum Flow Rate lines for the valve
orifices available.
8. Choose the orifice whose maximum flow rate exceeds
your requirements. If the point on the graph falls close tothe maximum flow rate for an orifice, you may choose
the next largest orifice number.
Note: The above procedure is provided as a reference guide to sizing the orifice
for most typical applications. To assure proper orifice size selection for the specificapplication conditions, particularly those where the procedure results in an orificeselection near the limit lines in the graph, please contact our Applications Engineers
for assistance in selecting the proper valve orifice.

Example 1
You want to control your process pressure at 5 psia, witha flow rate of 1000 sccm of N2. Your inlet pressure is
15 psig (30 psia) giving a differential pressure (delta P)
of 25 psi. Approximating your delta P as 30 psi gives anIndex Number value of 175. Drawing a vertical line on theOrifice Selection Chart at 175 indicates Orifice #2 would
be sufficient but Orifice #3 would be the best choice.
Example 2
You want to control a vacuum process at a pressure of
0.5 psia, with a flow rate of 2000 sccm of He. Your inlet
pressure is 15 psia, giving a differential pressure (delta P)
of 15 psi, resulting in an uncorrected Index Number valueof 90. The gas density correction for He is calculated as
N2 density/He density =1.250/0.179 = 2.6.

Multiplying 2.6 by 90 gives a density-corrected Index
Number of 234. Drawing a vertical line on the Orifice 		
Selection Chart at 234 indicates Orifice #3 would be thebest choice.

Specifications
PhysicalPressure Transducer Type		
Baratron Absolute Pressure		
Baratron Gauge Pressure
Pressure Ranges (Full Scales)			
Transducer Overpressure Limit
Orifice Full Scale Ranges			Maximum Differential Pressure		(consistent with transducer		
overpressure limit)
Control Mode
Performance
Pressure Reading		
Accuracy		Temp. Coefficients					Time Response
Pressure Control		Range		Accuracy		
Time Response
Environmental
Operating Temperature
Storage Temperature
ElectricalPower Required
Input/Output Signals
Connector
Cable Length
RFI Sensitivity
Trip Points		
Rated		Adjustable		
Hysteresis		Indicators
Compliance
MechanicalMaterials Exposed to Gas		
Standard		Optional
Leak Integrity		External		
Internal (through closed valve)1,2						Fittings
Dimensions
Weight640B
641B
10, 100, 1000 mmHg (Torr)
60, 100 psi
45 psia or 2x F.S., whichever is greater50, 200, 1000, 5000, 10000, 20000, 50000 sccm (nominal F.S.
flow rates for N2 with 15 psig on inlet and atm. on outlet)
150 psi for 50 to 10,000 sccm orifices
30 psi for 20,000 and 50,000 sccm orifices
Downstream standard; Upstream optional±0.5% of Reading (includes linearity, hysteresis, and repeatability)
Zero: ±0.02% of F.S./°C
Span: ±0.04% of Reading/°C<100 msec>2 to 100% of F.S.
±0.2% of F.S.
<1.0 sec (excluding system time constant)
0° to 50°C (32° to 122°F)-20° to 80°C (-4° to 176°F)±15 VDC ±5%, 200 mA max.
0-5 VDC standard; 0-10 VDC optional
15-pin male type “D”
100 ft. (30 m) max.
SAMA 33.1, 1-abc: <0.2% of F.S.
Two open-collector transistors
250 mA @ 30 VDC
1 to 100% of F.S.
3% of F.S.
Green LED’s on when actuatedCE316L S.S., 316L/VAR S.S., Inconel, Nickel
Viton®, Kalrez®, Kel-F®
<10-9 scc/sec HeElastomer valve: <10-4 scc/sec HeMetal valve: <1% of F.S. (N2 @ 1 atm. ∆P)
Kel-F valve: <0.5% of F.S. (N2 @ 1 atm. ∆P)
Swagelok® 4 VCR®, 8 VCR, or 1/4” Swagelok, Surface Mount1.5” (38.1 mm) x 4.88” (124 mm) (4 VCR) x 5.50” (140 mm) max.
2.54 lbs. (1.15 kg)

1640/641 Control Valves should not be used for positive shutoff. Where positive shutoff is required, a separate valve should be installed. When selecting the location of an
external shutoff valve, consideration should be given to the maximum pressure rating of the internal transducer and to the possibility that leakage across the internal valve overtime can build up and result in a sudden surge of gas. The 640 Series controllers require flow to operate, and cannot control pressure in “dead-ended” (zero flow) applications.

2

Leak specification “through closed valve” applies when the device is controlling pressure at its outlet which is the standard, as built configuration. If the device is to be configured
for controlling pressure at its inlet, the leak rate will be higher. Please consult with Applications Engineering to determine if special set up and testing is required.

Ordering Information
Ordering Code Example: 640B13TW1V42V

CodeConfiguration

Absolute or Gauge Pressure Controller
AbsoluteGauge

640B
641B

640B

Pressure Range Full Scale (Note: For other pressure units or ranges, please consult factory.)
10 Torr (mmHg)
11T
100 Torr (mmHg)
12T
1000 Torr (mmHg)
13T
60 psi61P
100 psi
12P
Fittings
Swagelok 1/4”		Swagelok 4 VCR male
Swagelok 8 VCR male
Surface Mount*
W-Seal (2787.3F)
C-Seal (2787.1)		

SW
T

Note: Unless otherwise specified,dimensions are nominal values in inches(mm referenced).

WH
C

Valve
Normally closed

1

1Seal Materials
Viton
Kalrez
Metal

V
DM

V

Valve Orifice # (nominal F.S. flow range for N2 at 1 atm. ∆P)A (50 sccm)
A#1 (200 sccm)
1#2 (1000 sccm)
2#3 (5000 sccm)
3#4 (10000 sccm)
4#5 (20000 sccm)
5#6 (50000 sccm)*
6

Dimensional Drawing —13T4Trip Points
With22

Valve Plug Material
Viton
KalrezMetal**Kel-FVDMFV*Larger differential pressures may be required for Full Scale Flow.					**Metal valve plug available on 200 sccm and larger valve orifice.
Optional Accessories
246C single-channel power supply/readout/set point control		
247D four-channel power supply/readout/set point control		
647C four-channel power supply/readout/set point control/RS-232
647C eight-channel power supply/readout /set point control/RS-232
Cables640/641 to 246, 247		
640/641 to 647 (includes open/close lines)		
Contact Applications Engineering for shielded cables for CE Compliance.
*Fitting options C and H are available only with metal sealed product versions

640/641B - 1/18		
© 2009-2018 MKS Instruments, Inc.
All rights reserved.

MKS Instruments, Inc.
Global Headquarters

MKS Instruments, Inc.
Valve 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:246C
247D
647C4R0N
647C8R0N
CB259-5-10
CB147-1-10

978.975.2350

MKS products provided subject to the US Export Regulations. Diversion or transfer contrary to US law is prohibited.
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 ofMKS Instruments, Inc., Andover, MA. Kel-F® is a registered trademark of 3M Company, Minneapolis, MN. Viton® and Kalrez®
are registered trademarks of E.I. Dupont Co., Inc., Wilmington, DE. Swagelok® and VCR® are registered trademarks ofSwagelok Marketing Co., Solon, OH.