Surfmaster discriminates or what?

[nelson]

Hi there.
Today i was trying to detect a small needle with surfmaster PI. So i made a small coil from network cable, wich has 230 uH and 1.2 ohms of resistance.
This coil has you will see on the video, can detect a very small pice of wire that cames from a resistor leg. Then i tryed to detect a bigger enameled copper wire that was imposible. Also i tryed a pice of needle that is used to inyect salt solution to meat and chikends. This needle is made of steel, not iron has i said in the video and this is also not detected. So my question is if surfmaster can do some kind of discrimination or what? The delay is set to 15 uS.
Now i whant to know if is possible to detect copper and steel, just by increasing the delay value?
Finally, does anyone knows if is posible to use surfmaster like a no movement detector by activating the pinpoint function?
The video is rigth here:
http://www.youtube.com/watch?v=ajuM0VX-U3A

Regards
Nelson

[Vortxrex]

Hi Nelson, is the needle made of stainless steel? I am surprised that it did not detect the copper wire ?

Dave Frank

[nelson]

Hi Vortxrex
Yes, the needle is made of stainless steel.
I m surprised too that it did not detect the copper wire.
My delay is setting to 15uS and the coil is made from network cable. No shield on the coil.
I havent try to detect a gold nugget, cause i don´t have any.
Regards
Nelson

Hi Nelson, is the needle made of stainless steel? I am surprised that it did not detect the copper wire ?

Dave Frank

[taliesin]

i saw the video interesting

could be used in surgical theatre's too.nelson have you tried it with a longer wires to the coil(coax) like 1m

[nelson]

Not jet, but i will try it later. This weekend i couldn´t continue my tests.
So far if anyone else can take the time to respond me what can cause that with this small coil, you detect some tiny wires and not the bigger ones?
Regards
Nelson

could be used in surgical theatre's too.nelson have you tried it with a longer wires to the coil(coax) like 1m

[DIRCEU]

|Hi! Nelson.


The Surfmaster can detect the small wire (from leads of a resistor) cause it's made with others metals.
Try to put a magnet near this small wire and you will see.
Try again with a small pure cooper wire (not leads).

Regards

Dirceu.

[taliesin]

just a thought

i've been thinking about the insulated wire test.perhaps the insulation prevents the static from your body contributing to the signal.try both with items on the end of varnished bamboo stick .

[mikebg]

Nelson, Surfmaster can not discriminate, despite there is a DISC knob. Surfmaster is most sensitive to ferrous metals, because it has all drawbacks of a classic PI metal detector: it uses monocoil and a demodulator wich subtracts integrals of two samples, the DISC knob shifts the delays of both samples.
IMNHO, Sr. Dirceu is near to truth.
The stainless needle and copper wire are nonferrous. They create weak signal because it is generated only by eddy currents flowing in very small loops.
Try with a magnet to see that it will attract your screw and your resistor lead. They create large signal because it is generated not only by eddy currents. The ferrous metal operates also as ferrite core.

[nelson]

Hi Dirceu

Ok, i will try it and post my results. I really can´t understand why this occur.
Regards
Nelson

|Hi! Nelson.


The Surfmaster can detect the small wire (from leads of a resistor) cause it's made with others metals.
Try to put a magnet near this small wire and you will see.
Try again with a small pure cooper wire (not leads).

Regards

Dirceu.

[taliesin]

just a thought

has the needle become magnetised at some point?

[nelson]

Nop, it hasn´t
Regards
Nelson

has the needle become magnetised at some point?

[maikl]

Nelson, Surfmaster can not discriminate, despite there is a DISC knob. Surfmaster is most sensitive to ferrous metals, because it has all drawbacks of a classic PI metal detector: it uses monocoil and a demodulator wich subtracts integrals of two samples, the DISC knob shifts the delays of both samples.
IMNHO, Sr. Dirceu is near to truth.
The stainless needle and copper wire are nonferrous. They create weak signal because it is generated only by eddy currents flowing in very small loops.
Try with a magnet to see that it will attract your screw and your resistor lead. They create large signal because it is generated not only by eddy currents. The ferrous metal operates also as ferrite core.

Hi mikebg. You say: "Surfmaster is most sensitive to ferrous metals, because it has all drawbacks of a classic PI metal detector ..." I think someone will get angry because a "lot of pushing Surfmaster".

[mikebg]

Maikl, I'm more angry
At the time when a professional designer begins a project, it must first examine what has been done in this area in the world so far. Even amateur designers are searching WEB and reading patents in order to improve a project.
I'm sure that when started to design the Surfmaster, its designers have not even read the patents issued so far at that moment. The principle of Surfmaster corresponds to knowledge for PI before half century.

[bklein]

Nelson, Surfmaster can not discriminate, despite there is a DISC knob. Surfmaster is most sensitive to ferrous metals, because it has all drawbacks of a classic PI metal detector: it uses monocoil and a demodulator wich subtracts integrals of two samples, the DISC knob shifts the delays of both samples.
IMNHO, Sr. Dirceu is near to truth.
The stainless needle and copper wire are nonferrous. They create weak signal because it is generated only by eddy currents flowing in very small loops.
Try with a magnet to see that it will attract your screw and your resistor lead. They create large signal because it is generated not only by eddy currents. The ferrous metal operates also as ferrite core.

This relates to a question I was going to post - the test for a good feedline is that it shouldn't be detected by the coil if swept by it. I was wondering about that - if that really is a good thing...

Barry

[Jose]

Hi all
Experiment with my homemade detector, with coil diameter and 28 cm in 17 usec delay. and does not detect a piece of copper wire.
Only copper wire detects section greater than 2 mm in diameter, close to the coil, with very low signal, so I conclude that the tests performed in the video, it is normal for a conventional PI detector.
Jose