  The commonest method of characterizing a cold field electron emitter is to
measure its current-voltage characteristics, and the commonest method of
analysing these characteristics is by means of a Fowler-Nordheim (FN) plot.
This tutorial/review-type paper outlines a more systematic method of setting
out the Fowler-Nordheim-type theory of cold field electron emission, and brings
together and summarises the current state of work by the authors on developing
the theory and methodology of FN plot analysis. This has turned out to be far
more complicated than originally expected. Emphasis is placed in this paper on:
(a) the interpretation of FN-plot slopes, which is currently both easier and of
more experimental interest than the analysis of FN-plot intercepts; and (b)
preliminary explorations into developing methodology for interpreting
current-voltage characteristics when there is series resistance in the
conduction path from the high-voltage generator to the emitter's emitting
regions. This work reinforces our view that FN-plot analysis is best carried
out on the raw measured current-voltage data, without pre-conversion into
another data format, particularly if series resistance is present in the
measuring circuit. Relevant formulae are given for extracting
field-enhancement-factor values from such an analysis.
