Watson Smith I/P Converters and Manostats


  • High Stability
  • Low Maintenance
  • Wide range of air supply options
  • Intrinsically safe versions available

The Watson Smith family of current to pressure(I/P) , Voltage to pressure (E/P) and precision regulators has led the way in technology in converting 4-20mA and 0-10V electrical signals to pneumatic signals of 0.2 to 1.0 bar and 3 to 15 psi. These devices are mainly used as the final electronic element in many control loops.

Type 100X for reliability at Low Cost
Type 140 for Hazardous area compatibility
Manostats for precision regulators



watson smith logo

Coulton instrumentation is proud to be the no.1 distributor for Watson Smith (based in Leeds, LS6 2RT England)

I/P Converters

Electronic I/P Converters

Type 422

Standard models currently in stock!

All electronic I/P converters have closed loop control, excellent vibration resistance, long term stability and can be mounted in any orientation.
4-20mA signal and a range of output variations.

Type 422 Freeze fail I/P converter


  • 3-15psi, 3-120psi, 0.2-1bar, 0.2-8bar output options
  • High Flow - 280 l/min (10scfm)
  • Faifreeze drift rate < 2% setpoint/hour
  • IP65 rating
  • Type N or Intrinsically Safe options

For price and delivery, please contact us !




Watson Smith type422



Electro Mechanical I/P

and E/P Converters Type 100X

Standard models currently in stock!

Rugged and reliable force balance converters for use in both process control and industrial applications.

Type 100X
Type 101X - Electro Mechanical E/P & I/P


  • 4-20mA, 0-10V; 0-60mA signal options
  • Pressure ranges from 3-15psig (0.2-1bar) to 3-120psig (0.2-8bar)
  • Two wire or three wire versions (12/24V)
  • High Flow - 280l/min (10scfm)
  • Weatherproof to IP65
  • Intrinsically safe versions available


Watson Smith type 100x





Electronic I/P Converter

Type 140

Standard models currently in stock!

Type 140 I/P Electronic Converter (Failsafe)

Robust, explosion-proof pressure converter with Triple Certification and IP66 & NEMA 4X weatherproofing. With ExN Certification.

For price and delivery, please contact us !



Watson Smith type 140


P/I Converters


P / I Converters

Type 68 P/I Converters

This instrument convert pneumatic pressure into electrical signals for use with data loggers, computers and microprocessors. The Type 68 is a two wire pressure/current device. This use only non-critical power supplies.

» 4-20mA, 0-10V output
» Wide range of input pressures
» DIN rail mounting
» Intrinsically safe option

List of available models: 680100, 680110, 68043X, 68066X, 681500, 681510, 68151X, 682100, 682110, 683300, 683350, 683500, 683510, 683600, 689610
Watson Smith type 68



71 P/I Converter


The Type 71 P/I instruments convert pneumatic pressure into electrical signal. It is a two wire device, uses non- critical power supply and is supplied to IP65. With Hazardous Area approved to ATEX, its encapsulated electronics makes it good for shock/vibration performance.

List of available models: 710101, , 710102, 712101, 712102

For price and delivery, please contact us !
Watson Smith type71






R27/Manostat Precision Pressure Regulator Range

The Manostat Precision Pressure Regulator Range are designed for critical pressure control applications and have demonstrated outstanding reliability in many thousands of applications worldwide.

It is suitable for dead-end (closed load) conditions and can be supplied on its own or with a visual display dial. The base unit has been developed to be operated by various mechanisms making it ideal for many different applications. Versions include: handwheel, plunger, lever operated and volume boosting air relay.


R27 / Manostat Manually Operated

These Manostats are available as Handwheel or Volume Boosting Air Relay operation options.

» Ideal for for dead-end (closed load) conditions and can be supplied on its own or with a visual display dial.
» Precise regulation of pressures up to 10 bar
» Control relatively independent of flow and temperature
» Ideal for dead end applications
» DIN/Dial versions for visual indication of set pressures.
» Low Air Consumption

Non extensive list of available models (all of the following are suitable replacement units for model starting with "53"): 100200R, 10024XR, 10025XR, 10026XR, 10044XR, 10045XR, 100300R, 100400R, 13009XR, 160300R, 200400R, 220400R, 240100R 300100R, 301200R, 301300R, 301400R, 309000R, 309100R, 31001XR, 31003XR, 310100R, 311200R, 311300R, 311400R, 319000R, 319100R, 329000R, 5310R0300R, 5310R0200R

Watson Smith manostat manual

R27 / Manostat Mechanically Operated

Options include Plunger, Lever and Volume Boosting Air Relay operation.

» Control relatively independent of flow and temperature.
» Precise regulation of pressures up to 10 bar
» Ideal for dead end applications
» Plunger/lever operation options available
» High relief capability
» Pressure range can be limited by resetting the locknuts provided
» A high relief version is avaiable for applications requiring a rapid exhaust.

Non extensive list of available models (all of the following are suitable replacement units for model starting with "53"): 180100R, 180200R, 180400R, 190100R, 190400R
Watson Smith manostat mechanical
R27/Manostat Auto/Manual Loading Stations

Remote manual and auto/manual loading stations are designed for the remote control of pneumatic systems using a manostat regulator and different combinations of air switching valve and pressure gauge.

» Remote control of pneumatic systems
» 3-way valve for bumpless air switching
» Horizontal and vertical mounting
» Weatherproof option available

Non extensive list of available models (all of the following are suitable replacement units for model starting with "53"): 359000R, 371201R, 379000R, 382100R, 391200R, 392100R, 393200R, 399100R, 399110R

For price and delivery, please contact us !
Watson Smith loading station


Pressure Meters

300D Pressure Meter

Type 300D Portable Precision Pressure Meter

The type 300D portable pressure meter is a digital unit designed for the calibration and test of pneumatic instruments and systems.

With Automatic Zero Calibration for added accuracy, a back-light for easy reading and standard set-up retention to ensure the last setting remains on the unit when re-powered.

» Hand/held and easy to operate
» Selectable units of pressure
» Battery operated, up to 200 hrs life
» Housed in robust plastic case


Watson Smith 300D Portable pressure meter


Flow Controller

Indicating Air Flow Controller Type Fri-30

The Type FRI-30 is an adjustable indicating air flow controller consisting of a differential regulator, needle valve and variable area flow meter. It is suitable for level control and air purge applications.

» Pressures up to 100psi
» Tamperproof cover
» Panel, upright mounting

Watson smith indicating air flow controller




Also available in limited options: The 122E Explosion Proof I/P Converter.

We can also supply suitable replacement units for obsolete Watson Smith I/P Converters such as the Type 421, Type 423, Type 425 and type 440. Please contact us for further information.



Are you looking for a new Watson Smith item, a replacement or just some advice? Not sure where to start? As the top UK distributor for Watson Smith we can help!

Just send us an enquiry or call us now on 01202 480 303 or email us at sales@coulton.com !

Sales Brochures

Manostat (950 KB)

Type 100x / 101X Datasheet

100X I/P (130 KB)

Type 422 Datasheet

Type_422_Datasheet (72 KB)

Type 140 Datasheet

Type 140 I/P (166 KB)

Manostats, P/I Converters and Other Datasheets

Fri_30_Datasheet_Flow_controller (85 KB)
Manostat_Manually_Op_Datasheet (179 KB)
Manostat_Mechanically_Op_Datasheet (159 KB)
Loading_Station_Datasheet (121 KB)
Type_68_Datasheet (131 KB)
ATEX_Type_71_Datasheet (180 KB)
Type_300D_Datasheet (68 KB)

Type 100x / 101X Instruction Manual

Type_100X_Instruction_Manual (582 KB)

Type 422 Instruction Manual

Type_422_Instruction_Manual (3481 KB)

Type 140 Instruction Manual

Type 140 I/P IM (681 KB)

Other Instruction Manuals

Price Lists

See also

Our range of valve positioners

A complete range of valve positioner including pneumatic, eletro-pneumatic and digital positioners.
PMV electropneumatic sub



"The supply and control of Liquid Nitrogen is critical to our Manufacturing process, so a recent breakdown completely disrupted our production runs.

Coulton Instrumentation were able to deliver a Watson Smith I/P converter in superfast time.
My initial phone enquiry was handled in a very efficient and helpful manner resulting in the placement of order, delivery, component installation and system restore all in under 6 hours.

No mean feat considering the M25 and 200 road miles in between!

My appreciation and thanks to all concerned"

Eddie P.
10th Jan 2013

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