JOURNAL OF MAGNETIC SHIELD CASE STUDIES

Will that be Cash, Check, Credit Card ... or Interference?
Case #19203

A major supplier of POS (point-of-sale) equipment discovered unacceptable problems with magnetic interference in its equipment. For those of you who still remember a cash register as the machine in a store that holds the cash, the retail world now demands that a POS terminal processes checks, credit cards, debit cards, electronic transaction authorization, and security control. (Older folks, take note: you still get to hand your cash, et al., to a real live person.)

One module of the POS terminal verifies a personal check by reading the preprinted account number. This module reads the numbers by sensing the magnetic ink that is used to print the checks. Because the read head must be very sensitive in order to detect this miniscule amount of magnetism, it may misread a check if interfering magnetic fields are present. Misreads cause frustration for both the sales clerk and the customer and may result in lost sales.

To ensure proper operation of the check reader module, the supplier tamed to Magnetic Shield Corporation.

The problem of eliminating interference at the read head was straightforward. A motor that rotated a drive wheel to pull the personal check through the reader was the primary source of magnetic interference. The supplier's engineers determined that a wrap of CO-NETIC AA Alloy perfection annealed foil was sufficient to eliminate the disturbance. Immediate shipments of stock foil enabled production and shipments of the terminals to proceed on schedule.

We improved on this solution by producing CO-NETIC AA Alloy foil blanks precisely cut at our factory to the required final size of the wrap part. This allowed the supplier to receive the part ready to use on its production line. During a visit from one of our factory sales managers, we learned that the supplier was incurring additional cost before installation because an adhesive backing had to be added to the foil to hold it in place around the motor. We then developed a process to apply the adhesive to the foil, butt cut it to the proper length, and coil it onto an oversize width carrier for convenient handling. The assembler simply removes the foil from the strip and immediately puts it in place.

We continue to work with this customer to design optimum shielding solutions for EMI protection of their new products.