Tuesday 8th March 2022 Customer success story WHY STANDARD PROXIMITY SENSORS JUST CAN'T COUNT Production counting or effective spoilage analysis demands accurate can counting. Recently a canmaker was alarmed to find that, on some processes, their outward product count was actually greater than the inward count! Something was clearly wrong. Sencon was asked to take a look at the customer's can counting system, which was using standard proximity sensors. CANS WITH THE JITTERS Counting beverage cans presents some particular challenges that standard proximity sensors are not really capable of coping with. It’s common to find cans that are being held effectively stationary on the conveyor while the belt continues to run underneath them. In this situation the cans will move about in front of the sensor, which can cause the sensor to continue to count the same can as it moves in and out of the sensor’s sensing field. This effect is known as ‘jitter’. Also, the variable bunching or spacing of cans on a conveyor makes it difficult for standard proximity sensors to achieve the correct sensing distance. The solution was to install Sencon’s intelligent count sensors which are able to overcome these issues. The counting heads on Sencon's Can Count Sensors have a unique ability to compensate for backing-up, jiggling, and bouncing without losing the correct count. The dual headed design also means that they have no trouble achieving the correct sensing distance whether the cans are tightly bunched or loosely spaced along the conveyor. A more subtle source of counting inaccuracy is related to the PLC program cycle time. Fast moving cans, which may also be located away from the face of the sensor will produce a short duration count pulse. This happens because it’s only the extreme peak of the can’s circumference that is detected. Also, it should not be forgotten that cans on air conveyors or gravity trackwork may move at velocities greater than the maximum rated production speed of a line. These short duration count pulses may at times be shorter than the PLC’s I/O cycle time, in which case they are missed from the overall count. Using the optional “divide-by” feature (1, 2, or 10) in Sencon can count sensors makes it possible to effectively stretch the output signals to an acceptable duration for programmable controller applications to process while maintaining a highly accurate count for production and spoilage analysis. Sencon can count sensors have a unique design which has been specially developed for the canmaking industry, they allow precisie monitoring of both production and spoilage rates and can give canmakers 100% confidence that the results obtained are accurate. For more information on Sencon's complete range of Line Control Sensors contact your regional Sencon office or agent.