Editing Steam engine (section)

=== Monitoring and control ===

[[File:Steam indicator (Steam and the Steam Engine - Land and Marine, 1875).jpg|thumb|upright=0.8|right|Richard's indicator instrument of 1875. See: Indicator diagram (below)]]

For safety reasons, nearly all steam engines are equipped with mechanisms to monitor the boiler, such as a [[pressure gauge]] and a [[sight glass]] to monitor the water level.

Many engines, stationary and mobile, are also fitted with a [[governor (device)|governor]] to regulate the speed of the engine without the need for human interference.

The most useful instrument for analyzing the performance of steam engines is the steam engine indicator. Early versions were in use by 1851,{{sfn|Hunter|Bryant|1991|p=123|loc = 'The Steam Engine Indicator' Stillman, Paul (1851)}} but the most successful indicator was developed for the high speed engine inventor and manufacturer Charles Porter by Charles Richard and exhibited at London Exhibition in 1862.<ref name="Thomson 2009" /> The steam engine indicator traces on paper the pressure in the cylinder throughout the cycle, which can be used to spot various problems and calculate developed horsepower.<ref>{{cite web
 |last1       = Walter
 |first1      = John
 |title       = The Engine Indicator
 |year        = 2008
 |url         = http://www.archivingindustry.com/Indicator/chapterzero.pdf
 |pages       = xxv–xxvi
 |url-status=dead
 |archive-url  = https://web.archive.org/web/20120310071206/http://www.archivingindustry.com/Indicator/chapterzero.pdf
 |archive-date = 10 March 2012}}</ref> It was routinely used by engineers, mechanics and insurance inspectors. The engine indicator can also be used on internal combustion engines. See image of indicator diagram below (in ''Types of motor units'' section).