Types of automatic weigher
A) Platform weighers
These are normally metal boxes, which are placed on the litter and are linked by a cable to a control box in the broiler house. They weigh one bird at the time and are self-tareing when no birds are on the scale. In other words the empty weight of the scale is zeroed each time to allow for build up of muck on the scale.
When a bird gets on the scale, the scale records a higher weight. It allows for oscillation in the recorded weight, and when the weight is stable, it will be recorded if it meets certain criteria. The weight has to be within a set percentage of the expected weight for that day. If it is not, (for example, if two or more birds go on the same time), the weight is discarded as not valid weight. These scales can give reasonable accurate estimates of the average weight.
Disadvantages of a platform weigher
1) The scale has to be empty of birds before the next bird weight is recorded. So if several birds stay on the scale for some time, no weighings are possible before they ALL get off!
2) The load cell and the electronic equipment in the platform weigher itself are near the litter where a build up of dampness and ammonia may take place. Over time, this can get into the electronics and cause failure.
3) A cable has to lead from the scale to the control box. At least part of this is on or under the litter, and can be damaged by birds or otherwise.