I/P and P/I Converter

Pressure measurement is very important factor in the process industries. For measuring the pressure and converting into electrical signal and transmitting it over the long distance for controlling purpose Pressure to Current (P/I) Converter is used.

Pneumatic signals is used to actuate pneumatic controllers like control valves and other pneumatic positioners particularly used in chemical and petrochemical industries where there is a fire risk. These actuators are controlled by electrical signals (current) from a controller like PLC or SCADA. For converting current signal into a pneumatic signal Current to Pressure (I/P) Converter is used.

Front Panel Diagram

Apparatus Required:

Compressor

Experiment 1:

To study characteristics of Pressure to Current (P/I) converter.

Procedure:

• Switch ON the compressor.
• Set G1 to 20 PSI by adjusting air regulator.
• Switch ON the unit.
• Connect panel ammeter to the P/I output terminals.
• Gradually increase the pressure (G3) from 0 to 15 PSI by opening HV1.
• Measure the output current (mA) for different pressures and tabulate them.

Note: Regularly open and close HV2 to ensure excess air removal.

Table 1:

Sl. no	Input Pressure (G3) PSI	Output current (mA)

Experiment 2:

To study the characteristics of current to pressure converter.

Procedure:

• Switch ON the compressor.
• Set G1 to 20 PSI by adjusting air regulator.
• Switch ON the unit.
• Connect panel ammeter to the I/P input terminals.
• Gradually increase the current from 4 to 20 mA by adjusting the knob.
• Note down the corresponding pressure readings (G2).
• Tabulate the readings.

Table 2:

Sl no	Input Current (mA)	Output Pressure (G2) PSI