Instrument Calibration Study Guide

Calibration compares an instrument or measurement system against a suitable reference so you can determine how closely the indicated or transmitted value matches the expected value.

Good calibration work includes preparation, reference equipment with suitable range and uncertainty, controlled test points, as-found and as-left records, and a clear tolerance decision.

A bench calibration proves the device itself; a loop check verifies the full path through wiring, barriers or isolators, I/O, controller scaling, HMI indication, alarms, and sometimes final control response.

• Record as-found data before making adjustments.
• Verify reference-standard range, resolution, accuracy or uncertainty, and calibration status.
• Separate zero error, span error, non-linearity, hysteresis, repeatability, and deadband.
• Use multiple test points across the calibrated range.
• Verify downstream scaling if transmitter output is correct but the control-system indication is wrong.