Surf PI Pro

[Qiaozhi]

Regarding No4 ... I have found that Coil calculator is not bad solution but in real life it can be wrong.

http://www.geotech1.com/forums/attachment.php?attachmentid=13817&d=1290969584

Used 0.4 mm copper enameled wire (that is 0.44 with layers of isolation)
in coil which is 23 cm and 24 turns.... calculator says more than measured.
coil calculator ... 0.93 mH

Try entering the correct value for the radius of 115mm, and not 230mm, which is the diameter.
For a radius of 115mm and 24 turns, the inductance is calculated as 417uH.

[sdesic]

Regarding No4 ... I have found that Coil calculator is not bad solution but in real life it can be wrong.

http://www.geotech1.com/forums/attachment.php?attachmentid=13817&d=1290969584

Used 0.4 mm copper enameled wire (that is 0.44 with layers of isolation)
in coil which is 23 cm and 24 turns.... calculator says more than measured.
coil calculator ... 0.93 mH

[Mohamed Ghitas]

High everyone this is my first contribution in this great forum
i almost read half of this thread but iam confused and need help
first i`d like to thank "ApBerg - bernet_one - sdesic - ..." for their help and of course Carl-NC

i need your help please in
1- I need schematic for PCB with its real size "99X68" i cant print the attached .jpg it is very big i need one with actual size.
2- Is this is the last edition for this detector ?? "SURF XX" .
3- Is there is any updates on SURF XX ??
4- I need coil 25cm diameter or more which kind of wire should i use also which diameter of wire and how many turns ??

thanks in advance

Mohamed Ghitas

[Tepco]

In most cases this is custom built part. You can machine missing shaft and add knob, but no need to mess with this, just set control to cal position ,when it clicks, maybe you will need to do this from inside and leave it, now volt\div will be calibrated to mach front panel marking, if sometimes need to be varied simply use another channel.

[multieagle]

One further question. The Ch2 Volts/Div Switch knob is broken. I can still adjust volts setting, but the 5x mag button is broken off and unusable. Guess the question is: in connection with testing metal detector projects, how often would one require magnification? Alternate question: are these type switches still available, or must they be scavenged off broken systems? See attached.

[multieagle]

Hey guys, thanks! I soaked the controls with Dynamite Magnum Force2 electronic cleaner and got the pots and switches operating smoothly. Redid the initial calibration test and got perfect square waveform. Now, just have to learn how to use it.

[Tepco]

Probably no need for repair shop. If you can get proper square wave with new probe and compensation works, at least sometime, but not always repeatable, problem may be simply in dirty\oxidized contacts on Volts\div switch inside the scope producing some intermittent failure, try to rotate it a bit to see if this is the case. Happens with old things, not used for longer period of time. You need to open the instrument, and then some patience and some contact spray can fix this easily.

[multieagle]

Thanks for the feedback. I purchased a new set of probes, and still get the same waveform, which outside of size and location adjustments does not change. It may be something loose inside, as playing with the dials, I did get a square waveform on probe#2. However was unable to reproduce it. Guess if I had some manner of waveform generator, could test it further. Thought about taking it into a repair shop for evaluation. Hate the thought of that, as unit cost could climb to well over a hundred bucks. Generally, these things often go for well under a hundred bucks. Granted, untested.

[TH Jim]

I've seen this type of waveform on bad probes too. A simple probe can be made with a large value resistor (10 Meg) and a small variable capacitor. Have a look on Google. You can put one together in 5 minutes and see what your waveform looks like then

Regards Jim.

[Tepco]

Most probably the probe. Faulty, not just uncompensated, waveform looks really bad, if probe is 1:10 switchable, maybe mechanical switch failure. Try to connect ordinary piece of wire from cal output to scope input, you have to get something square wave looking to isolate probe problem, most probably not scope failure. Vertical part of waveform will be invisible under normal conditions, just need to look like square. As both channels respond identically, scope failure is unlikely (or very serious)

[multieagle]

I purchased a Goldstar 20 mhz oscilloscope on eBay, supposedly in good working order. When I set it up according to the manual, and do the self test, I get the pattern shown below in the attached image. It is supposed to be a square pattern. Obviously, the vertical trace is not visible. Increasing the intensity does not help. Nor does calibrating the probe. I get the same pattern on both channels. Can anyone tell from the image whether it is the probe that is at fault, or the oscilloscope?

Gord

[dmq1219]

Hello YHL, Are you in Nanchang? Could you give a qq number or email to contact with you.?
Jason from Shenzhen

[liekwang]

jons

TlC 555 or NE555 is used and either is fine

[liekwang]

I use the Ndesis cable shielded with resistance 14omh 20 cm diameter instead of the copper wire coated with resin I love the sensitip of the metal but is also sensitive to land what if coil in swinging swinging this problem which I can not solve

[sdesic]

I think that this will help in making Surf Pi Pro coil.
Must try building fast coil.

Making a Fast Pulse Induction Mono Coil by Joseph J. Rogowski (bbsailor)

http://www.geotech1.com/cgi-bin/pages/common/index.pl?page=metdet&file=/projects/fastcoils/index.dat

Any feedback would be appriciated