| 摘要 |
Process for monitoring a passageway through which objects on carriers ( 12 ) are transported, such that the passageway is guarded by at least one light grid ( 16 ) with a plurality of light rays running one above the other, where the light grid ( 16 ) is divided into a first, lower area ( 16 a) through which the carriers ( 12 ) pass and a second, upper area ( 16 b) through which the objects pass, which light grid ( 16 ) possesses an evaluating circuit which emits a signal if a light ray ( 22 ) is interrupted in the first, lower area ( 16 a) and provides information on the height of the object, which process comprises by the following steps: a) storage of the current value for the height as last measured value b) readout of the first, lower area ( 16 a) of the light grid ( 16 ) to determine whether a carrier ( 12 ) has passed through the light grid ( 16 ) and readout of the second, upper area ( 16 b) of the light grid ( 16 ) c) determination of a new current value for the height of the object from the data read out from the second, upper area ( 16 b) of the light grid ( 16 ) d) setting of an object flag to indicate that an object is located within the light grid ( 16 ) if the last measured value has a value of zero within a range of tolerance and the current measured value differs from zero within a range of tolerance, cancellation of the object flag if the last measured value differs from zero within the tolerance range and the current measured value has a value of zero within the tolerance range, and determination of whether the object flag has been changed e) setting of a carrier flag when a carrier ( 12 ) is detected in the first, lower area ( 16 a) of the light grid ( 16 ) and cancellation of the carrier flag when no carrier ( 12 ) is detected in the first, lower area ( 16 a) of the light grid and no object flag is set f) examination of whether the current measured value and the last measured value satisfy a predetermined condition and reversion to step a) if this is the case and if a carrier flag is set g) return to step a) when the carrier flag is set and the object flag was changed h) execution of the security function when a light ray ( 22 ) from the second, upper area ( 16 b) of the light grid ( 16 ) is interrupted.
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