| 摘要 |
The method is used for electrical current measurement, especially for measuring a temporally varying small current. The current to be measured is subjected by a control system to an opposite-polarity compensation current having approximately the same magnitude, the magnitude of the current to be measured being determined according to the compensation current and the measured current. A reverse-biased photodiode (15) is used for controlling the compensation current, which photodiode is controlled by an amplitude-modulated and frequency-modulated light source (14). In addition to the optical decoupling, which is achieved thereby, of the control loop this method has the advantage that, because of the linearity of the optoelectrical coupling component (14, 15), a linear measurement range of nine decades can be achieved, without it being necessary to have external changeover of the measurement range. <IMAGE>
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