Hall effect sensorA Hall effect sensor (or simply Hall sensor) is a type of sensor which detects the presence and magnitude of a magnetic field using the Hall effect. The output voltage of a Hall sensor is directly proportional to the strength of the field. It is named for the American physicist Edwin Hall. Hall sensors are used for proximity sensing, positioning, speed detection, and current sensing applications. Frequently, a Hall sensor is combined with threshold detection to act as a binary switch.
Noise dosimeterA noise dosimeter (American English) or noise dosemeter (British English) is a specialized sound level meter intended specifically to measure the noise exposure of a person integrated over a period of time; usually to comply with Health and Safety regulations such as the Occupational Safety and Health (OSHA) 29 CFR 1910.95 Occupational Noise Exposure Standard or EU Directive 2003/10/EC. Noise dosimeters measure and store sound pressure levels (SPL) and, by integrating these measurements over time, provide a cumulative noise-exposure reading for a given period of time, such as an 8-hour workday.
External fixationExternal fixation is a surgical treatment wherein Kirschner pins and wires are inserted and affixed into bone and then exit the body to be attached to an external apparatus composed of rings and threaded rods — the Ilizarov apparatus, the Taylor Spatial Frame, and the Octopod External Fixator — which immobilises the damaged limb to facilitate healing. As an alternative to internal fixation, wherein bone-stabilising mechanical components are surgically emplaced in the body of the patient, external fixation is used to stabilize bone tissues and soft tissues at a distance from the site of the injury.
Apothecaries' systemThe apothecaries' system, or apothecaries' weights and measures, is a historical system of mass and volume units that were used by physicians and apothecaries for medical prescriptions and also sometimes by scientists. The English version of the system is closely related to the English troy system of weights, the pound and grain being exactly the same in both. It divides a pound into 12 ounces, an ounce into 8 drachms, and a drachm into 3 scruples of 20 grains each.
External auditorAn external auditor performs an audit, in accordance with specific laws or rules, of the financial statements of a company, government entity, other legal entity, or organization, and is independent of the entity being audited. Users of these entities' financial information, such as investors, government agencies, and the general public, rely on the external auditor to present an unbiased and independent audit report. The manner of appointment, the qualifications, and the format of reporting by an external auditor are defined by statute, which varies according to jurisdiction.
History of measurementThe earliest recorded systems of weights and measures originate in the 3rd or 4th millennium BC. Even the very earliest civilizations needed measurement for purposes of agriculture, construction and trade. Early standard units might only have applied to a single community or small region, with every area developing its own standards for lengths, areas, volumes and masses. Often such systems were closely tied to one field of use, so that volume measures used, for example, for dry grains were unrelated to those for liquids, with neither bearing any particular relationship to units of length used for measuring cloth or land.
