METAL DETECTORS – What is the purpose of Notch Discrimination?
A. Notch Discrimination can be used to either reject a narrow band of targets (notch reject) or to respond only to a narrow band of targets (notch accept). It is usually used to reject pull-tabs while still finding nickels and the gold rings which do not have the same phase response as pull-tabs. The Notch Level control generates a “window signal,” whose width is set by a small control on the PC board. This “notch window” can be moved up and down the discriminate range, until it properly covers the desired range of target response. If the detector is being used to eliminate the response to pull-tabs, you need to remember that any good target with phase response which fall within the window will also be eliminated. Such targets consist mainly of gold items and rings. The notch accept feature can be used to tune the detector to a particular type of item, such as a known type of ring. The detector then will only find items which fall within the narrow notch window.
