REVERSE DISCRIMINATION

[kt315]

http://lucaslab.grandhost.pl/lucaslab/wykrywacz_PI.htm

[6666]

http://lucaslab.grandhost.pl/lucaslab/wykrywacz_PI.htm

Thanks Kt315

[daverave]

would using a mini oscilloscope on the pulse detector show ferrous or maybe a large piece of iron or coke can ????

[kt315]

dabbo did.

Dear all, sorry for my English. Today I want to show my homemade metal detector . Surf pi 1.2. I added a mini oscilloscope to view the eddy current . In this way easily I recognize the iron. Greetings to all dabbo1974

[daverave]

[ATTACH]34107[/ATTACH][ATTACH]34108[/ATTACH][ATTACH]34109[/ATTACH]

Hi kt315
in the schematic that you show it has a meter...does this only really work on large pieces of iron or cans using a later sample...i guess it cannot id small nails or wire...im i correct in my assumption ???

[daverave]

i might try that mini oscilloscope idea...i think maybe only useful on the larger iron and cans ???

[kt315]

do you not see larger iron by your surf? why you are not able

to contradistinguish

strong signal from pale signal?

small gold gives faded short tiny sound. it is NOT the discrimination?

[daverave]

if i get surface iron i get a double blip if horizontal....but i find deep iron can come through like small signal....i guess ive not learnt to distinguish different metals with the surf pi.

[kt315]

using a later sample --- maybe a discovery now i open for you but all reaction signal decay brings full info about a metal+soil. you may take any part of decay (sample) for disc, what you personally guess it useful.

[daverave]

Hi kt315
thanks for the diagram...does the needle on the analogue meter swing negative on iron cause late sample is inverted ????

[kt315]

yes it is later sample, schematic demonstrates this clearly. looks you have to tune a pot of the module keeping a coil on ground, so needle would be in 'zero' (middle) position you set. then measurement will be more less optimistic precise.

inverted or not - rechange wires on microAmpermeter and you will get right measurement - left GREEN sector ferrous, right RED sector gold and silver.

[daverave]

does this design work on the size of the object rather than the ferrous content ????

[kt315]

if you did hunt with VLF you would be noticed - big size ferrous object sounded like good unferrous.
so you have to exclude from view this size of object. we say about 'bottle cap' size object.

[daverave]

i just ordered the mini oscilloscope kit that you showed...i dont really have extra room in my surf pi housing for extra electronics for another sample circuit...so i will try the oscilloscope method but i will have to get a project box with a transparent window for the scope...not sure if i can a ready made one ???

[6666]

KT315, do you know what current rating the analogue meter should be ?