Electronic weighing apparatus

Abstract

An electronic weighing apparatus comprises a slit plate provided to be displaceable in association with the weight of an article being placed on a weighing pan. A photosensitive device is provided in the vicinity of the split plate for generating a train of pulses responsive to the slits in association with the displacement of the slit plate. The slits are provided on the slit plate such that the pulses are obtained from the photosensitive device only if and when the amount of displacement exceeds that corresponding to a predetermined weight value. The slit plate is further provided with a magnetic shield plate at the position before the photosensitive device detects the slits for the first time when the slit plate is displaced by virtue of an article. A permanent magnet and a reed switch are provided to be faced to each other through the slit plate at a mechanical zero point position, such that the reed switch is turned on if and when the slit plate is displaced and the magnetic shield plate is removed from the mechanical zero point position, whereby various components of the electronic weighing apparatus are energized by a battery. The pulse train obtained from the photosensitive device is counted by an up/down counter, which is initially loaded with the data associated with the above described predetermined weight value when the reed switch is turned on. Accordingly, the up/down counter starts a count operation of the pulse train, starting from the above described initial count value associated with the above described predetermined weight value.