Glossary · Sensors and measurement
Accuracy
Also known as: Sensor accuracy, Instrument accuracy
German: Genauigkeit
In sensor and instrument specifications, accuracy states how close the output of a sensor or instrument comes to the true value of the measured quantity, usually as a maximum error in percent of span, of the measured value or in engineering units.
- Sensors
In one sentence
Accuracy states how close a sensor's output comes to the true value, usually as a maximum error in percent or engineering units on the datasheet.
Example
A pressure transmitter datasheet specifies an accuracy of 0.1 % of span at reference conditions, plus separate temperature effects.
How it applies
- Engineering: Datasheet accuracy usually applies to reference conditions. The error in the field adds temperature effects, long-term stability, installation effects and the error of the signal chain. Compare devices only when the reference of the percentage is the same: percent of span, of upper range value or of reading.
- Commissioning: A loop check against a reference confirms that the installed chain works as specified; it does not replace Calibration.
- Documentation: Always state the reference of an accuracy figure. Write 0.5 % of reading or 0.5 % of span, never just 0.5 %.
Accuracy vs. precision
Accuracy is about closeness to the true value. Precision is about closeness of repeated readings to each other. A sensor can be precise but inaccurate, for example when it has a constant offset. In metrology, accuracy is a qualitative concept; quantitative statements are made with errors and Measurement uncertainty.