Keysight E1412A, User'S Manual And Scpi Programming Manual, Page: 222 / 243

ccxxii Keysight E1412A Digital Multimeter User Guide
E1412A Multimeter Specifications Interpreting Multimeter Specifications
Accuracy
Accuracy is a measure of the “exactness” to which the multimeter's
measurement uncertainty can be determined
relative to the calibration reference
used. Absolute accuracy includes the multimeter's relative accuracy
specification plus the known error of the calibration reference relative to national
standards (such as the U.S. National Institute of Standards and Technology). To
be meaningful, the accuracy specifications must be accompanied with the
conditions under which they are valid. These conditions should include
temperature, humidity, and time.
There is no standard convention among multimeter manufacturers for the
confidence limits at which specifications are set. The table below shows the
probability of non-conformance for
each specification with the given
assumptions.
Variations in performance from reading to reading, and instrument to instrument,
decrease for increasing number of sigma for a given specification. This means
that you can achieve greater actual measurement precision for a specific
accuracy specification number. The E1412A is designed and tested to meet
performance better than mean

4 sigma of the published accuracy
specifications.
Transfer Accuracy
Transfer accuracy refers to the error introduced by the multimeter due to noise
and short-term drift. This error becomes apparent when comparing two
nearly-equal signals for the purpose of “transferring” the known accuracy of one
device to the other.
24-Hour Accuracy
The 24-hour accuracy specification indicates the multimeter's relative accuracy
over its full measurement range for short time intervals and within a stable
environment. Short-term accuracy is usually specified for a 24-hour period and
for a

1°C temperature range.
Specification Criteria Probability of
Failure
Mean  2 sigma 4.5%
Mean  3 sigma 0.3%
Mean  4 sigma 0.006%