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在金属检测装置中,涡流检测仪也已如同周末盖革计数器一样普及;现在,人们就象购买销钉那样,可方便地从国内的五金器械商店买到它们。多年前,人们建立了涡流检测理论,阐明了电磁场与金属间的相互作用。涡流或电磁检测通常由三个部分组成,即载交流电流的线圈,计测电流的仪表和被检的金属部件。线圈通交流电流后产生垂直于电流方向或平行于线圈轴的交变磁场,在金属部件接近线圈时磁场便发生变化。如果此金属部件是非磁性的,则在部件中感生方向垂直于磁场的涡流;涡流又产生一个反对线圈原始磁场的磁场,导致部分原磁场抵消,使通过线圈的磁通减小而使线圈阻抗发生变化。涡流检测的实质,就是监测线圈阻抗的变化。检测线圈的特性一般由两个电阻抗值表示:
Eddy current testers have also become as popular as weekend geiger counters in metal gauges; they are now readily available from hardware stores in the country like pins are purchased. Years ago, people established the eddy current testing theory, clarifying the interaction between the electromagnetic field and the metal. Eddy current or electromagnetic detection is usually composed of three parts, namely, carrying the current coil, measuring current meter and the seized metal parts. The alternating current from the coil produces an alternating magnetic field perpendicular to the direction of the current or parallel to the axis of the coil. As the metal part approaches the coil, the magnetic field changes. If the metal part is non-magnetic, eddy current is induced in the part perpendicular to the magnetic field; the eddy current again generates a magnetic field against the original magnetic field of the coil, resulting in the partial cancellation of the original magnetic field and the decrease of the magnetic flux passing through the coil, Change. The essence of eddy current testing is to monitor changes in the impedance of the coil. The characteristics of the detection coil are generally represented by two electrical impedance values: