Electro-pneumatic converter or I to P converter is one, which accepts 4 -20mA current (I) as input and converts into linear air pressure (P) in the range of 3-15 PSI. In process control, instruments, all the transmitter/receiver's outputs and inputs, are normally in the range of 4-20mA. (4mA are least value (0%) of FSD and 20mA is maximum value (100%) of FSD. A change in this current is used to indicate a change in flow, level, temperature, pressure, viscosity, load, speed, velocity etc. Hence, there is a need to have Electro-pneumatic converters from any of the above parameters to pressure and vice-versa. For example opening a valve and closing a valve. This valve in turn may allow air, water, oil, slurry etc to pass in controlled quantities. Hence, there exists a need to study what this Electro-pneumatic converter is all about. Electro-pneumatic converter experimental demonstration instrument consists of: 1) A stand alone 4-20mA current simulator. This simulator provides adjustable current in range of 4-20mA. A current meter monitors this. A selector switch selects either current from this simulator or from an external current source, operated by any other current source. 2) An Electro-pneumatic converter operating in the range of 3-15 PSI. Two pressure gauges connected on either side monitor upstream and down stream pressures. It is necessary to provide stabilized compressed air pressure as input, from any standard compressor. The upstream (from the compressor) pressure is more or less stable, while the down stream (from this converter) pressure keeps changing between 3 to 15 PSI, proportional to the current input to this converter. 3) This pressure can be monitored by a pressure gauge. I-P converter characteristics can be studied by tabulating the output pressures for various current inputs for forward travel (i.e. from 3 to 15 PSI) and backward travel (i.e. from 15 to 3 PSI). Therefore hysterisis can be plotted; the accuracy and linearity of the converter can be determined.

Specifications:

• Input: 4-20mA current
• Output: 3-15PSI (0.2 to 1Kg/cm2).
• I/O threads: 1/4" NPT
• Zero and Span adjustment by screw adjuster.
• Coil resistance: 90(+/-) 5 ohms.
• Coil inductance: 10mH.
• Supply pressure: 1.4Kg/cm2
• Air consumption: 60Litres/Hr.
• Vertical mounting
• Dial gauge at upstream.
• Pressure vessel with pressure release valve.
• All pneumatic connections are made by using FESTO or similar make quick couplings.
• Current meter: To monitor input to I-P converter.
• Built-in DC power supply.
• Selector switch to monitor current from internal current generator or from any external source.
• Pneumatic line to be provided by the user from any standard compressor, at 5kg/cm2.