Tolerance in Measurement Systems

Tolerance is a term that is closely related to accuracy and defines the maximum error that is to be expected in some value.

Even as it is not, strictly speaking, a static characteristic of measuring instruments, it is mentioned here because the accuracy of some instruments is sometimes quoted as a tolerance figure. When used correctly, tolerance describes the maximum deviation of a manufactured component from some specified value.

For instance, crankshafts are machined with a diameter tolerance quoted as so many microns (10-6 m), and electric circuit components such as resistors have tolerances of perhaps 5%. One resistor chosen at random from a batch having a nominal value 1000W and tolerance 5% might have an actual value anywhere between 950W and 1050 W.