Static characteristics of Sensor

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 Static characteristics of Sensor:

It is about how the output of a sensor changes in response to an input change after steady state condition.


Accuracy: Accuracy is the capability of measuring instruments to give a result close to the true value of the measured quantity. It measures errors. It is measured by absolute and relative errors. Express the correctness of the output compared to a higher prior system. Absolute error = Measured value – True value

Relative error = Measured value/True value

Range: Gives the highest and the lowest value of the physical quantity within which the sensor can actually sense. Beyond these values, there is no sense or no kind of response.

e.g. RTD for measurement of temperature has a range of -200`c to 800`c.

Resolution: Resolution is an important specification for selection of sensors. The higher the resolution, better the precision. When the accretion is zero to, it is called the threshold.

Provide the smallest changes in the input that a sensor is able to sense.

Precision: It is the capacity of a measuring instrument to give the same reading when repetitively measuring the same quantity under the same prescribed conditions.

It implies agreement between successive readings, NOT closeness to the true value.

It is related to the variance of a set of measurements.

It is a necessary but not sufficient condition for accuracy. 

Sensitivity: Sensitivity indicates the ratio of incremental change in the response of the system with respect to incremental change in input parameters. It can be found from the slope of the output characteristics curve of a sensor. It is the smallest amount of difference in quantity that will change the instrument’s reading.

Linearity: The deviation of the sensor value curve from a particularly straight line. Linearity is determined by the calibration curve. The static calibration curve plots the output amplitude versus the input amplitude under static conditions. 

A curve’s slope resemblance to a straight line describes linearity.

Drift: The difference in the measurement of the sensor from a specific reading when kept at that value for a long period of time.

Repeatability: The deviation between measurements in a sequence under the same conditions. The measurements have to be made under a short enough time duration so as not to allow significant long-term drift.

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