Military Some instruments, such as telescopes and sea navigation instruments, have had military applications for many centuries. However, the role of instruments in military affairs rose exponentially with the development of technology via applied science, which began in the mid-19th century and has continued through the present day. Military instruments as a class draw on most of the categories of instrument described throughout this article, such as navigation, astronomy, optics, and imaging, and the kinetics of moving objects. Common abstract themes that unite military instruments are seeing into the distance, seeing in the dark, knowing an object's geographic location, and knowing and controlling a moving object's path and destination. Special features of these instruments may include ease of use, speed, reliability, and accuracy. Uncategorized, specialized, or generalized application Actograph measures and records animal activity within an experimental chamber. Densitometer measures light transmission through processed photographic film or transparent material or light reflection from a reflective material. Force platform measures ground reaction force. Gauge (engineering) A highly precise measurement instrument, also usable to calibrate other instruments of the same kind. Often found in conjunction with defining or applying technical standards. Gradiometer any device that measures spatial variations of a physical quantity. For example, as done in gravity gradiometry. Parking meter measures time a vehicle is parked at a particular spot, usually with a fee. Postage meter measures postage used from a prepaid account. S meter measures the signal strength processed by a communications receiver. Sensor, hypernym for devices that measure with little interaction, typically used in technical applications. Spectroscope is an important tool used by physicists. SWR meter check the quality of the match between the antenna and the transmission line. Universal measuring machine measures geometric locations for inspecting tolerances. Alphabetical listing See also :Category:Instrument-making corporations Data logger measuring devices History of measurement History of weights and measures Instrumentation List of measuring devices List of physical quantities List of sensors Metrology Pocket comparator Sensor or detector Timeline of temperature and pressure measurement technology Wikipedia:WikiProject Physics/Worklist of central experiments Notes The alternate spelling "-metre" is never used when referring to a measuring device. References External links Metrology