Static
Characteristics of Measuring Instruments
About the static characteristics of
measuring instruments
If we have a thermometer in a room and
its reading shows a temperature of 20°C, then it does not really
matter whether the true temperature of the room is 19.5°C or 20.5°C.
Such small variations around 20°C are too small to affect whether we
feel warm enough or not. Our bodies cannot discriminate between such
close levels of temperature and therefore a thermometer with an
accuracy of ±0.5 °C is perfectly adequate. If we had to measure the
temperature of certain chemical processes, however, a variation of
0.5°C might have a significant effect on the rate of reaction or even
the products of a process. A measurement accuracy much better than
±0.5°C is therefore clearly required.
Accuracy of measurement is thus one consideration in the choice of
instrument for a particular application. Other parameters such as
sensitivity, linearity and the reaction to ambient temperature changes
are further considerations. These attributes are collectively known as
the static characteristics of instruments, and are given in the data
sheet for a particular instrument. It is important to note that the
values quoted for instrument characteristics in such a data sheet only
apply when the instrument is used under specified standard calibration
conditions. Due allowance must be made for variations in the
characteristics when the instrument is used under other conditions.
More Instrument Classification
|