A. Terminology
1. Span : the range of measured variable that a sensor can measure.
2. Least-count : the smallest difference of measured variable that can be detected by a sensor.
3. Readability : the closeness with which the scale of a sensor can be read in analog output. A sensor with a 30 cm. scale would have a higher readability than a sensor with a 15 cm. scale and the same span. In digital output, readability will be the relative size of the letters.
4. Sensitivity : the change in output of the sensor with the unit change in input variable to be measured; e.g., if a 1-mV recorder has a 5 cm scale length, its sensitivity would be 5 cm/mV.
5. Accuracy : the change in output of a sensor from a known measured input. Accuracy is usually expressed as a percentage of full scale reading; e.g., a 100-kpa pressure transducer having an accuracy of 1% would be accurate within +-1 kPa over the entire range.
6. Precision : the ability of a sensor to reproduce a certain output with a given accuracy.
The difference between precision and accuracy : Consider the measurement of a known