Description of the problem

With these encoders, in contrast to other encoders, the absolute position, i.e. the number of revolutions, is not mechanically recorded with the aid of a gear unit, but is stored in a battery-backed memory. If the power supply to the encoder fails when the servo drive is switched off, because the battery is empty or the connection to the battery is interrupted, the encoder irrevocably loses the absolute position. In order to prevent possible damage to an axis, this case must be taken into account and given special treatment. The displayed error must not be able to be acknowledged with the normal error reset. To do this, there must be a way to reset the error and re-reference the axis and put it into operation after battery power is restored to the encoder.