Glossary · Sensors and measurement
Measured value
Also known as: Measured quantity value, Measurement result
German: Messwert
In metrology, a measured value (measured quantity value) is a quantity value that represents a measurement result, consisting of a number and a unit. A complete measurement result also states its measurement uncertainty.
- Sensors
- Standards
In one sentence
A measured value is the number and unit that represent a measurement result; complete results also state the measurement uncertainty.
Example
The HMI displays the measured value 4.73 bar for tank pressure; the calibration certificate of the transmitter gives the associated uncertainty.
How it applies
- Engineering: In control systems, a measured value travels with metadata: engineering unit, timestamp and a quality or status flag. Without these, downstream functions cannot tell whether the value is current and valid.
- Operation: A measured value can be valid, uncertain or bad, for example after a Sensor break. Operators should see this status, not just a frozen number.
- Data: Historians and analytics need the unit, the source and the sampling time of each measured value to compare data correctly.
- Documentation: Interface specifications and operating instructions should name measured values consistently, with unit and range. Separate the measured value (actual value) from setpoints and calculated values.
Measured value vs. true value
A measured value is what the measuring system reports. The true value is unknown in principle; the Measurement uncertainty describes the range in which it reasonably lies.