Probe for Garrett Sea Hunter

[Buzz(ID)]

My Finished Probe

Here is my Finished Probe ,suspended in spray foam insulating sealant and wraped coil in rubber cable splicing form Radio Shack and used epoxy made by Super Glue called Plastic Fusion for the pipe end also heat shrink wires several times.The number of wire turns was 68 of 22 AWG and as for the pipe I used sch 1120 PVC 3/4"

Buzz

[rgecy]

Buzz,

Nice looking probe! What size ferrite cores did you use and how many? What detector is this for?

Robert in SC

[Buzz(ID)]

Thanks Robert , The ferrite rod 12.3 mm(approx 1/2 inch) only used one, the core was 2 1/2 inches long and double wraped the end with which for makes for a stronger field. The Goldquest. I need to get a LCR meter but on ohms it read .7 This was a mod on a probe I had . I was only getting 3 inches and now 5 inches.

Buzz

[Carl-NC]

Yesterday I built a third probe with a 1/2" rod, about the same as Buzz. 64 turns for 300uH. Performance was about the same as my 3/16" probe.

"Also, is there a way to make the sides of the coil less sensitive and keep the tip sensitive?"

This has to do with the permeability of the ferrite rod. I suspect most ferrite rods are not particularly high quality. Also the length-to-diameter ratio affects field focus. So what you probably want are long skinny ferrite rods with high permeability. However, this might also reduce the end-field, I don't recall.

Which leads me to another thought... making the ferrite rod. Ferrite rods are just iron powder and epoxy. Would be nice to make the exact dimensions I want, namely to fit down the core of a fibreglass tent pole. Anyone know a source of powdered iron? Might be able to use black sand.

- Carl

[bbsailor]

PI Probe Material

Here is a good link to learn about soft ferrites that are good for PI probes.
http://www.intalek.com/Index/Project.../MA012000a.pdf

I just wound a PI probe using a 8" long X .5" diameter ferrite material 43 from Surplus Sales of Nebraska. Save your money, it does not work for a PI probe. This rod is detected when I wave it near my 11" mono coil.... not good!

Ferrite material that that starts with the digit 3 indicated that the material is managanese zinc...good for a PI probe. Surplus Sales of Nebraska has a .281" diameter X 1.969" long rod, soft ferrite material 3C80 that works well.

Ferrite material that starts with the digit 4 indicated that the material is nickel zinc... not good for a PI probe.

Hopefully, this will save some curious PI probe experimenters from wasting their money.

Now, if I could find a 3C80 (or similar) ferrite rod .5" X 4", that would make a probe with a little more detecting range than the smaller rod mentioned above.

bbsailor

[Buzz(ID)]

Here is a good link to learn about soft ferrites that are good for PI probes.
http://www.intalek.com/Index/Project.../MA012000a.pdf

I just wound a PI probe using a 8" long X .5" diameter ferrite material 43 from Surplus Sales of Nebraska. Save your money, it does not work for a PI probe. This rod is detected when I wave it near my 11" mono coil.... not good!

Ferrite material that that starts with the digit 3 indicated that the material is managanese zinc...good for a PI probe. Surplus Sales of Nebraska has a .281" diameter X 1.969" long rod, soft ferrite material 3C80 that works well.

Ferrite material that starts with the digit 4 indicated that the material is nickel zinc... not good for a PI probe.

Hopefully, this will save some curious PI probe experimenters from wasting their money.

Now, if I could find a 3C80 (or similar) ferrite rod .5" X 4", that would make a probe with a little more detecting range than the smaller rod mentioned above.

bbsailor

Hi BB
If I knew the ratio of the metals I could probably make them, I have access to a small foundry. Is this a composition ceramic mix?

Buzz

[Buzz(ID)]

Here is a good link to learn about soft ferrites that are good for PI probes.
http://www.intalek.com/Index/Project.../MA012000a.pdf

I just wound a PI probe using a 8" long X .5" diameter ferrite material 43 from Surplus Sales of Nebraska. Save your money, it does not work for a PI probe. This rod is detected when I wave it near my 11" mono coil.... not good!

Ferrite material that that starts with the digit 3 indicated that the material is managanese zinc...good for a PI probe. Surplus Sales of Nebraska has a .281" diameter X 1.969" long rod, soft ferrite material 3C80 that works well.

Ferrite material that starts with the digit 4 indicated that the material is nickel zinc... not good for a PI probe.

Hopefully, this will save some curious PI probe experimenters from wasting their money.

Now, if I could find a 3C80 (or similar) ferrite rod .5" X 4", that would make a probe with a little more detecting range than the smaller rod mentioned above.

bbsailor

I guess I should have done a little research before I posted that last post.
You can buy manganese in rods, chips etc. As far a zinc I wonder if one can grind the two a make a compound with exopy as Carl was talking about?
Manganese is very falmeable so I guess the foundry bad idea is out unless you like rockets.


Buz

[Qiaozhi]

Hi BB
If I knew the ratio of the metals I could probably make them, I have access to a small foundry. Is this a composition ceramic mix?

Buzz

Try here -> http://www.gredmann.com/div/divh.htm
Might be worth sending them an email.

[rgecy]

Carl,

OK. I now have my Oscilloscope and wanted to check out my probe. What exactly am I looking for? What kind of reading should I see?

How do I interpret what the Oscope is telling me? Damping resistor etc.?

By the way, thanks, I adjusted it and got a good reading on the 1V square wave.

Thanks again.

Robert in SC

[Carl-NC]

Try probing the leads of the coil, you should see a pulse that peaks at 100 volts or more. Try it without a damping resistor, you should see a lot of ringing right after the pulse. Try a 220-ohm damping resistor, the ringing should go away and you get a nice smooth decay. Go to 470-ohms and the decay should shorten, but still be smooth. At some point, as you increase the damping R, the post-pulse decay will start overshooting, and you've gone too far.

- Carl