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Watson Smith - Controlling Pressure Worldwide
Type 425 Failsafe Electronic Converter
Current to Pressure (I/P)


 Advanced electronic control
 Explosion proof and intrinsically safe versions
 Failsafe operation (output pressure falls
    to minimum on power failure)
 Vibration immune
 Weatherproof General Description

The 425 proportional I/P converter uses advanced closed loop electronic control to achieve accurate, high resolution pressure control. It is available in explosion proof and intrinsically safe versions and its vibration immunity and weatherproofing make it ideal for field application.

Type 425 Failsafe Electronic I/P Converter

Functional Symbol

Technical Data
*Output Signal 0.2-1bar (3-15psig); minimum outlet pressure less than 15mbar (0.2psig)
*Air Supply Oil free, dry air, filtered to 5 microns; 1.3-4bar (18-60psig)
*Flow Capacity Up to 300Nl/min (10scfm)
*Air Consumption 0.6 l/min typical (0.02scfm) typical
*Response Time 5 seconds (from 10 to 90% or 100 to 10% of output pressure into a 0.5 litre load)
*Total Error +/-0.25% of span (typical, independent error includes the combined effect of non-linearity, hysteresis, deadzone and repeatability
*Temperature Effect Typically less than +/-1% span between -10°C and +60°C
*Supply Sensistivity Less than 1% span for 10% supply pressure change
*Connections 1/4" NPT female standard (plus two integral 1/4" NPT gauge ports)
*Operating Temperature -40°C to +85°C
*IP Rating IP66, NEMA 4X (when mounted upright)
*Vibration Output pressure changes less than 1% for vibration amplitude 5mm 10-30Hz, 10g 30--500Hz
*Electromagnetic Compatibility Compliant and CE marked in accordance with the EC E.M.C. directive. Tested to standards: BS EN50082-2: 1995, BS EN50081-2: 1994
*Material of Construction Aluminium and zinc diecasting with nitrile diaphragms, black epoxy powder coating standard
*Mass 930g
*Mounting Position Integral bracket allows for surface or 50mm pipe mounting in any orientation. Note: the unit must be mounted upright to achieve the weatherproof ratings
*Electrical Signal 4-20mA (two wire); load presents 6 volts (+/-0.5V) constant voltage drop to the current source
*Failure Mode Signal falls to below 15mbar (0.2psig) when input signal fails
*Tight Shut-off A potentiometer setting causes the output to fall to zero at between 3.2 and 4.5mA
*Connections 1/2 NPT or M20 female; internal terminal block with capacity up tp 2.5mm2 cable
All instruments are tested on the Watson Smith Automatic Testing System and an individual test certificate is provided at no extra charge. Each unit is tested for linearity, hysteresis, total error, settling error, over pressure, air consumption, response time, calibration, insulation, start-up current, supply sensitivity and voltage load.

Ordering Information





Type 425 Brochure

Models in this range include the 53AF2101, 53AF0132, 53AF0121, 53AF2133, 53AF2134, 53AF2123, 53AF0127, 53AF0111, 53AF2111, 53AF2129, 53AF0130, 53AF2128 and the 53AF0115.

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