时间：2011-03-11 23:11来源：蓝天飞行翻译 作者：admin 点击：次
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D’Arsonval meter (electrical measuring instrument). One of the most widely used types of direct-current measuring instruments. In a D’Arsonval meter, a small coil carrying the current to be measured is mounted on pivots and suspended in the field of a permanent magnet. A pointer is attached to the coil, and the rotation of the coil is restrained by two calibrated hairsprings. Current flowing through the coil produces a magnetic field that reacts with the field of the permanent magnet, and the coil rotates against the opposition of the hairsprings. The greater the current flowing through the coil, the stronger its magnetic field and the farther the coil rotates. A pointer attached to the coil moves across a scale calibrated in amps, milliamps, or microamps. D’Arsonval meters can be connected into circuits with multiplier resistors or shunts and can be used to measure voltage, current, or resistance. dashpot. A pneumatic or hydraulic dampener used to cushion or slow down mechanical movements. A loose-fitting piston moves back and forth in a cylinder which contains a fluid, either liquid or air. The piston is connected to the component whose movement is to be damped. The component can move slowly with little opposition if the fluid is given time to move from one side of the piston to the other, but the dashpot restrains fast movement because of the time it takes to transfer the fluid from one side of the piston to the other. A shimmy damper used on the nose wheel of a tricycle-gear airplane is a form of dashpot. data. A term that refers to all the facts available about a situation or project. Data can be accumulated and changed into a form usable in a computer. The computer then processes the data to produce records and projections. The word data is actually the plural form of datum, but it is often used as though it were singular. data base (computer operation). The body of information available on any particular subject. All Airworthiness Directives issued by the Federal Aviation Administration are contained in a data base. This allows a person performing an inspection on an aircraft to access, or tap into, this data base and get a list of all of the ADs that pertain to the particular aircraft, its engines, and components. data bus. A wire or group of wires used to move data within a computer system. data-plate performance (gas turbine engine performance). Performance specifications of a gas turbine engine that were determined in the manufacturer’s test cell when the engine was calibrated. This information, recorded on the engine data plate includes the engine speed at which a specified EPR is attained. When trimming the engine, the technician uses this data as the goal. datum. A reference from which measurements are made. For example, mean sea level is a datum for measuring true altitude, and the freezing point of pure water is a datum for measuring temperature. datum (aircraft location). An imaginary vertical reference plane or line chosen by the aircraft manufacturer from which all arms used for weight and balance computation are measured. |
