AUTOMATIC MAGNETIC ABNORMALITY DETECTOR

摘要

PURPOSE:To automatically detect magnetic abnormality free from the effect of amplitude variation and low frequency drift of a magnetic field measuring signal by automatically changing threshold according to a specified movement means thereof. CONSTITUTION:A digital magnetic field measuring signal U from an A/D converter 1 undergoes a Hear conversion with a Hear converter section 2 to calculate a Hear spectrum which is applied to a discriminator section 5. This signal U is also applied to a threshold calculating section 4. The calculating section 4 calculates a movement means of amplitude of the signal U during a certain time, square of deviation in the signal U with respect thereto and a movement means of the square of the deviation during a certain time to determine the threshold, which is set for the decision section 5 automatically varying the threshold according to amplitude variation of the signal U and a low frequency drift. This enables automatic detection of magnetic abnormality excellently free from the effect of the amplitude variation and the low frequency drift of the measuring signal.