Glossary · Sensors and measurement
Linearity
Also known as: Linearity error, Nonlinearity
German: Linearität
In measurement technology, linearity describes how closely the characteristic curve of a sensor or instrument follows a straight line between input and output; the linearity error is the maximum deviation from that line, usually in percent of span.
- Sensors
In one sentence
Linearity describes how closely a sensor's output follows a straight line over its range; the linearity error is the largest deviation from it.
Example
A load cell datasheet states a linearity error of 0.02 % of rated output, determined with the best-fit straight line method.
How it applies
- Engineering: Linearity figures depend on the reference line: terminal-based (through zero and full scale) or best-fit straight line. Best-fit figures look smaller, so compare devices only on the same basis.
- Commissioning: Nonlinear sensors such as thermocouples, RTDs or tank volumes are linearized in the transmitter or controller with standard tables or characteristic curves.
- Calibration: Multi-point calibration reveals nonlinearity that a two-point zero and span check cannot show.
- Documentation: State the method behind a linearity figure and where linearization is applied. Linearizing twice, in both the transmitter and the controller, is a common configuration error.
Linearity vs. accuracy
Linearity is one component of the total error. Accuracy also includes Hysteresis, Repeatability, temperature effects and offset.