| 摘要 |
In the method in accordance with the integrating phase comparison principle of measurement, the difference voltage (U) of a voltage (UL) derived from the line voltage and a voltage derived from the line current and called image voltage (UZ) is formed. Square wave voltages (Fig. 7a) having identical zero crossings are generated for the difference voltage (U) and for the image voltage (UZ) in square wave generators (3, 4) and the non-overlap time (TINT) between the image voltage and the difference voltage is determined in a section (6) and evaluated to decide the distance by comparison with a threshold value. To prevent wrong triggering in the case of distortion in the voltage quantities, all non-overlap times which occur during one half wave period of the image voltage are added together in an integrator (7) and the aggregate value is compared with the threshold value of the threshold section (8) releasing the distance decision. <IMAGE> |
