I/P Converter Output Calculator

The I/P Converter Output Calculator helps you quickly convert between 4–20 mA electrical signals and 3–15 psi pneumatic signals, which are standard in industrial instrumentation for driving control valves and positioners.

You can enter either the current (mA) or the pneumatic pressure (psi) and the tool will calculate the corresponding value, along with percent of span, making it useful for calibration, troubleshooting, and loop checks.

Use this I/P Converter Output Calculator whenever you:

• Calibrate an I/P converter or control valve positioner

• Check loop behavior between DCS/PLC output and valve

• Verify that controller output corresponds to correct pneumatic pressure

Introduction

1. Select Input Mode:

   • “From 4–20 mA → 3–15 psi” if you know the current and want the pneumatic output.

   • “From 3–15 psi → 4–20 mA” if you know the pneumatic output and want the equivalent current.

2. For mA → psi, enter only the Input Current (mA) field (e.g., 12.0 mA).

3. For psi → mA, enter only the Input Pressure (psi) field (e.g., 9.0 psi).

4. Click Calculate.

5. The result box will show:

   • Equivalent current (mA)

   • Equivalent pneumatic pressure (psi)

   • Percent of span (%)

   • A warning if the input value is outside the standard 4–20 mA or 3–15 psi range.

🧭 How to Use

1. Example 1 – From 4–20 mA → 3–15 psi

   • Mode: From 4–20 mA → 3–15 psi

   • Input Current = 12.0 mA

   Manual check:

   • mA span = 20 − 4 = 16 mA

   • Percent of span = (12 − 4) / 16 = 8 / 16 = 0.5 = 50 %

   • Pressure span = 15 − 3 = 12 psi

   • Output pressure = 3 + 0.5 × 12 = 3 + 6 = 9 psi

   Expected results:

   • Equivalent Current: 12.00 mA

   • Equivalent Pressure: 9.00 psi

   • Percent of Span: 50.0 %

2. Example 2 – From 3–15 psi → 4–20 mA

   • Mode: From 3–15 psi → 4–20 mA

   • Input Pressure = 6.0 psi

   Manual check:

   • psi span = 12 psi

   • Percent of span = (6 − 3) / 12 = 3 / 12 = 0.25 = 25 %

   • mA span = 16 mA

   • Output current = 4 + 0.25 × 16 = 4 + 4 = 8 mA

   Expected results:

   • Equivalent Current: 8.00 mA

   • Equivalent Pressure: 6.00 psi

   • Percent of Span: 25.0 %

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FAQ

Q1. What is an I/P converter?

An I/P (Current-to-Pressure) converter converts a 4–20 mA electrical signal into a 3–15 psi pneumatic signal to drive control valves and positioners.

Q2. Why are 4–20 mA and 3–15 psi used?

They are industry-standard ranges that provide good resolution, noise immunity, and a live-zero (4 mA / 3 psi) to distinguish between zero signal and a fault (broken wire or air failure).

Q3. Can I use this calculator for reverse-acting I/P converters?

This calculator assumes a linear direct-acting relationship. For reverse-acting (e.g., 4 mA = 15 psi, 20 mA = 3 psi), you would need to invert the mapping

Q4. What does “Percent of Span” mean?

It represents the position within the operating range.
0 % = 4 mA / 3 psi, 100 % = 20 mA / 15 psi.