CLAMP-ON AMMETER

摘要

C A N A D A TITLE : CLAMP-ON AMMETER INVENTOR : AURELE J. BLAIN The clamp-on ammeter consists of an iron core which extends to form a loop surrounding the conductor to be measured,and a moving coil which is caused to vibrate or rotate is placed in a gap in said core so that the voltage induced in the moving coil, by the flux, will correspond to the current being measured. For DC measurements an AC voltage is applied to a coil around the core to produce an alternating flux in the core to neutralize errors caused by residual magnetism, in the core. A means for increasing the range of the clamp-on ammeter consisting of another coil around the core and a current through the coil which produces a flux in the core that cancels the flux produced by the conductor current and the current in the said coil can be applied in various steps so that the meter will have various ranges. For AC current measurements a coil is wound around the core and the output of said coil is rectified and applied to a reading device,however, due to residual magnetism in the core the output of the coil will be non-linear. To correct this a capacitor is connected across the coil and the value of the capacitor is large enough to act as almost a short across the coil. The action of the capacitor causes the output of the coil to appear linear. Furtermore, the capacitor acts as a low resistance across the coil and a large current flows in the coil and the flux produced by said current tends to cancel the flux produced by the conductor and this greatly increases the meter range. Furthermore, the non-linearity of the rectifier diode is overcome by means of a transistor.