| 摘要 |
<p>When measuring current in a conductor (6), the two inputs of a differential amplifier (1) are connected to the conductor at two points (7, 8) which have a suitable spacing. This obviates dissipating elements in the measurement as well as use of current encircling elements. The power supply for the differential amplifier is tapped symmetrically with respect to the potential of the conductor. The voltage of the conductor is measured in addition to the current, and both current and voltage are fed to A/D converters. The digitized signals are fed to a calculation unit (5) which is adapted to calculate the instantaneous power of the conductor, its instantaneous energy, the square on the current of the conductor, the curve shape of the current and the frequency contents. The above-mentioned measurement set-up lends itself for the control of relays, fuse cut-outs, excess current specifications, as a consumption meter, for motor controls, and for amplifier characteristic monitoring.</p> |
