NOTE 1 Null measurement uncertainty is associated with a null or near zero indication and covers an interval where one does not know whether the measurand is too small to be detected or the indication of the measuring instrument is due only to noise.

NOTE 2 The concept of 'null measurement uncertainty' also applies when a difference is obtained between measurement of a sample and a blank.

ANNOTATION (informative) [2 December 2014] Here "measured quantity value" can be replaced by "measured value" without ambiguity: "measurement uncertainty where the specified measured value is zero".