Method and apparatus for improving readhead performance

Abstract

The present invention features a method and a fixture for determining the asymmetrical character of a readhead prior to its installation in a check-validation machine. Such a machine that is used to validate checks uses a stepper motor drive to convey the check past the readhead. The magnetic field produced by the coil of the stepper motor interferes with the capability of the readhead to recognize the magnetic indicia on the check. Once determined, the asymmetrical sensitivity of the readhead towards the magnetic flux allows the manufacturer to mount the readhead with its sensitive side away from the stepping motor of the validating unit. The readhead asymmetry is determined by the method of this invention by measuring an output voltage pulse of the readhead, when it is excited by magnetic pulses both forward and rear of its read gap. The excitation is provided approximately one inch from the read gap. The exciting pulses are of similar magnitude and timing as that of the signal field generated by the slip drive of the stepper motor. The peaks of the forward and rear output pulses are converted into DC voltage levels, which are then fed into a comparator circuit. The comparator circuit controls the lighting of a 'go/no go' indicator LED, which tells the operator which side of the readhead is more sensitive to the magnetic flux.