Electricity supply meter with protection against tampering - has device to detect and compensate for the influence of foreign magnetic field using shorted turns

摘要

The meter is protected against using a magnet to slow down the rotation of the meter disc, by incorporating a device (8, 9) whic responds to a foreign magnetic field to impart an additional moment of rotation to the disc. This device may have a short-circuited additional winding (8) coupled in the voltage supply system of the counter with a spring blade contact (9) acting as the short-circuit switch. The additional winding is wound around one limb of an M-shaped core (2). The number of winding turns is matched to the loading of the short-circuit contact (9) so that the effect of the foregin field had a reduced negative effect on the error curve. The additional winding (8) imparts a phase shift to the voltage flow.