An ultrasonic sealing apparatus comprises at least one horn having an elongated sealing face for sealing a packing material. In such embodiments, the apparatus also includes a processor operatively coupled to the optical detector, where the processor can calculate a metric value of the optical signal without an extinction ratio of the optical signal being measured. The discharge period covers spill valve closing period and spill valve opening period. The shutoff system may also be magnetically actuated to allow for dry testing in which the automatic shut-off functionality is testing without dispensation of fluid. The processor can include a virtual register translation look-aside buffer for tracking the location of each set of virtual register values associated with each context.