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Seen using a magnet to test EF. Wondered if magnet type matters. Charted two Neodymium magnets and a ceramic(ferrite .5 inch OD x 3/16 inch thick) magnet. The ceramic magnet had a signal during coil charge but didn't show a change during coil decay. All show a signal change when waving over coil testing for EF. The Neodymium magnets would be detected with a fast PI. Thinking a ceramic magnet is best for checking EF cancelling.
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Do you have a flexible fridge magnet to try ? -
Tried a 3.5x5inch flexible fridge magnet. Weak magnet. Fair signal when coil charging, no signal during decay. Prior tests looking at amplifier out on the bench circuit. Tried the magnets with my metal detector. Panel meter reading, integrator out(integrator direct coupled from amplifier), magnet and coil stationary. The ceramic and fridge magnet didn't change the reading from no magnet to the magnet laying on the coil. The Neodymium magnet(B) caused a change over 10 inches away(coil and magnet stationary). Looking at post amplifier out, capacitor coupled from integrator. Threshold set for no indication(led lights for indication). Swinging the coil or the fridge magnet placed on the coil and moved away fairly fast didn't cause the led to light. The ceramic magnet did. I have a pot on the input of the integrator to adjust for EF. It was adjusted for the ceramic magnet not causing an indication but something must have drifted. Have to try and readjust it.Originally posted by 6666 View PostComment
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