Compensating for noise, delays and imbalance in the output signal of a metal detector

摘要

A set of adjustments for compensating for noise or delay in the output signal of a metal detector is determined by a) measuring 176 the output signal in the presence of ferrite between the coil system at a given frequency, b) digitally adjusting 179 the output signal so that the output signal in a first or second component of the output signal is equal to or below a first predetermined threshold value and the output signal a second or first component of the output signal is above a second predetermined threshold value, the first component being out of phase with respect to the second component at a predetermined phase angle c) storing 180 the adjustments in a database or a look-up table; and d) repeating 174, 184 steps a, b and c for different frequencies. Also disclosed is a method of a) generating an adjustable balance signal, b) combining the adjustable balance signal with the output of the detector, and c) varying the adjustable balance signal to provide a compensated signal. The metal detector can be used to detect metal contaminants in food products.