I/P converter calibration

Introduction

Current to pressure converter (I/P) converts an analog signal (4 to 20 mA) to a proportional  pneumatic output (3 to 15 psi).It is one of the main pneumatic instruments used in industries. The most common application of I/P converter is to receive an electrical signal from a controller and provide proportional pneumatic output to control a positioner or a control valve.

Equipments needed

I/P converter, milliamp source,pressure source(20 psi),master gauge.

Note: no need of external power supply (24vdc)for working (neither for calibration)

Procedure of  I/P converter calibration

Generally I/P converter is calibrated for standard industrial signals as 4-20 mA input and 3-15 psi output.

Refer following steps to calibrate I/P converter:

1. Remove the I/P from the process.
2. If there is any top cover in I/P remove it.
3. Connect 20-psi supply pressure and connect a milliamp source to the I/P .
4. Set the input signal to 4 mA and check the output pressure on gauge as 3 psi.
5. If the pressure is showing more or less than 3 psi then adjust zero.
6. Turn zero adjustment screw slowly by very small turn to obtain 3-psi pressure. More turning of zero adjustment may damage the I/P converter.
7. Counter clockwise rotation increases the pressure, and clockwise rotation decreases the pressure.
8. Set the input current signal to 20 mA and check the output pressure on gauge as 15 psi.
9. Turn the span adjustment potentiometer very slowly by small turn to obtain 15-psi pressure. More turning of span adjustment may damage the I/P converter.
10. Repeat step 4 to check that the desired low value (4 ma ~ 3 psi) has not changed after adjusting the span. If necessary repeat from steps 3
11. Reconnect the I/P in the process.

Calibration of P/I converter.