Sensitivity of an electromagnetic type metal detector is directly related
to stability, the higher the required sensitivity, the more frequently
the rebalancing controls will have to be adjusted. Thus, for maximum sensitivity
in the head ,the use of automatic drift compensation network is necessary
in order to cancel out the signal resulting from a slow drift in the
coil system due to the temperature changes. The imbalance signal, although
small in the head itself, gives rise, after amplification, to a large unwanted
signal.
The purpose of this article is to indicate how drift correction technique
can be applied to a 100 KHz electromagnetic field type metal detector.
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