Calibration · Glossary

What is Hysteresis?

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Hysteresis is the difference between readings at the same input when approached from below (upscale) and from above (downscale).

Hysteresis Explained

Friction, mechanical play and material effects make an instrument read differently depending on the direction of change. Calibrations test both up and down to reveal it.

Mechanical gauges and switches show more hysteresis than electronic transmitters.

Hysteresis Formula

Hysteresis = max |R_up − R_down| ÷ Span × 100

R_up, R_down

readings at the same point rising and falling

Example: At 50 %, up 5.02 bar and down 5.06 bar on 10 bar span: 0.4 % of span.

Calculators for Hysteresis

CalculatorHysteresis CalculatorFree online calculator with formula and worked example.CalculatorCalibration Test Points GeneratorFree online calculator with formula and worked example.

Free Downloads

Free downloadPressure Transmitter Calibration Report FormatFree download in Excel and PDF.Free downloadCalibration Certificate Format in ExcelFree download in Excel and PDF.

Frequently Asked Questions

What is Hysteresis?

Hysteresis is the difference between readings at the same input when approached from below (upscale) and from above (downscale).

Should I tap a gauge before reading?

Many procedures allow light tapping to reduce friction; follow your procedure and record it.

Why must I not overshoot a test point?

Overshooting and returning reads the other branch of the hysteresis loop.

Learn more on the blog

Instrumentation calibration and troubleshooting guide

A practical guide on instrumentationblog.in with more detail on hysteresis and how it is applied on real plants.

Read Full Article

More Calibration Terms

Calibration termZero and Span ErrorZero and span error describe an instrument whose reading is offset at the bottom of the range (zero) or…Calibration termMeasurement UncertaintyMeasurement uncertainty is a quantified range around a result within which the true value is expected to…Calibration termType A and Type B UncertaintyType A and Type B uncertainty are the two ways of evaluating uncertainty: Type A from statistics of…Calibration termCoverage FactorCoverage factor k multiplies the combined standard uncertainty to give an expanded uncertainty at a…Calibration termTest Uncertainty RatioTest uncertainty ratio compares the tolerance of the instrument under test with the uncertainty of the…Calibration termGuard BandA guard band tightens the acceptance limit inside the tolerance to allow for calibration uncertainty,…

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