1. Accuracy

Accuracy refers to the degree of closeness of measurements of a quantity to that quantity’s true value. It is often expressed as a percentage of the full-scale value or in the units of the measurement.

The equation to calculate accuracy is:

Accuracy = (True Value-Measured Value) / True Value  x 100%

In instrumentation engineering accuracy is measured in two ways :
One is full scale value and other is measured value

A full scale value takes the full range of the device for example from 0-100m³Now the accuracy is +-1% of FS
Implies: for 30m³/hr it will be
29m³/hr or 31m³/hr

Now the other is measured value taken at a certain point
i.e.
for 30m³/hr +-1% of MV is
30.3m³/hr Or 29.7m³/hr