Accuracy

All Geokon vibrating wire sensors are calibrated against standards with an accuracy of ±0.1% Full Scale (FS) accuracy traceable to NIST (National Institute of Standards and Technology). Therefore all the data points on the calibration sheets are accurate to ±0.1% FS.

Linearity

The accuracy of the linear calibration factor supplied with the sensors depends on how closely the data points fall onto a straight line. Linearity is a measure of this closeness. Practically all sensors have linearities better than ±0.5% FS. Most sensors have linearities close to ±0.1% FS, and some exhibit linearities better than ±0.1% FS.

The point to remember is that the calibration points are all accurate to ±0.1% FS but the linearity may not be as good.

It should be noted that ±0.1% FS accuracy can often be achieved by fitting the calibration data points to a second order polynomial equation instead of to a straight line.

Sensitivity

Sometimes accuracy is confused with sensitivity: sensitivity refers to “How small a change in the measured parameter can the sensor detect and measure?” As a rule of thumb, for Geokon VW sensors, sensitivity is 1/4000th part of the range, i.e. 0.025% FS. Once you know the range you can figure out what the sensitivity is. Sensitivity is also known as resolution.

Precision

Precision is a measure of the repeatability of the sensor: i.e. when the measurand (the physical property being measured) is constant and the sensor is read repeatedly, it is the closeness with which the readout numbers agree with one another. The repeatability of Geokon Vibrating Wire sensors is usually ±1 readout digit, i.e. ±0.025% FS—the same as the sensitivity. The nice thing about such a high precision is that it allows small changes in the measurand to be measured very accurately, which is sometimes important.

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