the total luminous flux of a light source, which can then be measured by a photometer Densitometer for measuring the degree to which a photographic material reflects or transmits light Color: colorimetry Tristimulus colorimeter for quantifying colors and calibrating an imaging workflow Radar brightness: radiometry Synthetic Aperture Radar (SAR) instruments measure radar brightness, Radar Cross Section (RCS), which is a function of the reflectivity and moisture of imaged objects at wavelengths which are too long to be perceived by the human eye. Black pixels mean no reflectivity (e.g. water surfaces), white pixels mean high reflectivity (e.g. urban areas). Colored pixels can be obtained by combining three gray-scaled images which usually interpret the polarization of electromagnetic waves. The combination R-G-B = HH-HV-VV combines radar images of waves sent and received horizontally (HH), sent horizontally and received vertically (HV) and sent and received vertically (VV). The calibration of such instruments is done by imaging objects (calibration targets) whose radar brightness is known. Hearing Loudness in phon Headphone, loudspeaker, sound pressure gauge, for measuring an equal-loudness contour of a human ear. Sound level meter calibrated to an equal-loudness contour of the human auditory system behind the human ear. Smell Olfactometer, see also Olfaction. Temperature (sense and body) Body temperature or core temperature Medical thermometer, see also infrared thermometer Circulatory system (mainly heart and blood vessels for distributing substances fast) Blood-related parameters are listed in a blood test. Electrocardiograph records the electrical activity of the heart Glucose meter for obtaining the status of blood sugar. Sphygmomanometer, a blood pressure meter used to determine blood pressure in medicine. See also :Category:Blood tests Respiratory system (lung and airways controlling the breathing process) Spirometer Concentration or partial pressure of carbon dioxide in the respiratory gases Capnograph Nervous system (nerves transmitting and processing information electrically) Electroencephalograph records the electrical activity of the brain Musculoskeletal system (muscles and bones for movement) power, work of muscles Ergometer metabolic system Body fat meter Medical imaging Computed tomography Magnetic resonance imaging Medical ultrasonography Radiology Tomograph, device and method for non-destructive analysis of multiple measurements done on a geometric object, for producing 2- or 3-dimensional images, representing the inner structure of that geometric object. See also: :Category:Physiological instruments and :Category:Medical testing equipment. Meteorology See also :Category:Meteorological instrumentation and equipment. Navigation and surveying See also :Category:Navigational equipment and :Category:Navigation. See also Surveying instruments. Astronomy Radio antenna Telescope See also Astronomical instruments and :Category:Astronomical observatories.