5-Point Calibration Calculator (0–25–50–75–100% Table)

How to use the 5-point calibration calculator

Enter the calibrated input range (LRV and URV) and the output range (4 and 20 for a 4–20 mA transmitter, 1 and 5 for a 1–5 V signal). The calculator gives the input to apply and the output you should read at 25, 50 and 75%; the 0% and 100% points are the range ends you entered. Record the measured values and check each one with the calibration error calculator.

Calibration point formula

Input_p = LRV + p × (URV − LRV)  ·  Output_p = O_low + p × (O_high − O_low)

where p = 0, 0.25, 0.5, 0.75 and 1.

Example: 0–10 bar pressure transmitter

Point	Input	4–20 mA output	1–5 V output
0%	0 bar	4.00 mA	1.00 V
25%	2.5 bar	8.00 mA	2.00 V
50%	5 bar	12.00 mA	3.00 V
75%	7.5 bar	16.00 mA	4.00 V
100%	10 bar	20.00 mA	5.00 V

Calibration procedure

1. Isolate the transmitter, connect the pressure source and a reference gauge, and connect a multimeter or calibrator in the loop.
2. Apply each point upscale (0 → 100%) and record the output, then repeat downscale (100 → 0%).
3. Calculate the error at each point as % of span. If any point is out of tolerance, adjust zero and span and repeat to record as-left data.
4. For DP flow transmitters with square-root extraction, the output at 25% DP is 50% flow — see the DP flow square-root calculator.

Frequently asked questions

Why calibrate at five points?

Zero and span alone only fix the ends of the range. The 25, 50 and 75% points show non-linearity, and testing upscale then downscale reveals hysteresis.

What are the 5 calibration points for a 4–20 mA transmitter?

4, 8, 12, 16 and 20 mA, corresponding to 0, 25, 50, 75 and 100% of the calibrated input range.

Does the table work for a suppressed or elevated zero?

Yes. Enter a negative LRV for an elevated range (for example −50 to +150 mbar) and the input points are spaced across that range.

What about reverse-acting outputs?

Enter the output high value as the low and vice versa (for example 20 and 4) — the expected outputs then decrease as the input rises.

Related calculators

• Calibration Error Calculator (% of Span, As-Found / As-Left)Calculate instrument calibration error as a percent of span and of reading, and check as-found or as-left results against the tolerance.
• 4–20 mA Scaling CalculatorConvert a 4–20 mA loop current to a process value (and back) for any measuring range — with live scaling chart.
• Signal Converter Calculator (4–20 mA ↔ 0–10 V ↔ 1–5 V)Convert between 4–20 mA, 0–20 mA, 0–10 V and 1–5 V analog signals and percent of range — for transmitters, PLCs and signal isolators.
• Instrument Accuracy Calculator (% of Span vs % of Reading)Convert instrument accuracy between % of span, % of full scale and % of reading — and find the measurement error at any point in the range.
• 4–20 mA Loop Resistance Calculator (Maximum Loop Load)Check whether a 4–20 mA loop has enough voltage — maximum loop resistance from supply and transmitter lift-off voltage, with cable and barrier resistance.
• DP Level Transmitter Range Calculator (Wet Leg and Dry Leg)Calculate LRV and URV for a differential pressure level transmitter on open, dry-leg or wet-leg tanks — with zero elevation and suppression.

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