I have an application that requires that I sense a metal ball (approx 0.5" dia) inside a glass tube. We have been using inductive prox sensors but their cost and size has required that we revisit this design. Can anyone suggest a simple ckt or an ic that will perform this function. 12dc power and a TTL o/p would be ideal but we can work around any changes if needed.
PS. The tube is filled with a thick black liquid.