Frequency Tester I Tossed Together

[kac]

Came across a small circuit for relaying the frequency of a coil to a computer using a microphone jack and some software. I have a scope which will do the same thing but has to be hard wired to the coil or control board of the detector. What I liked about the circuit is it didn't need to be wired to the scope but the scope doesn't supply power to a circuit so I added a battery and then a couple leads to hook to the scope. I printed the little coil on my fdm printer and wound the coil on it.

Layed out the part in pcb software and printed the circuit on some silicone transfer paper then transferred and etched my own pcb. Soldered in the parts and tested it. Lastly I was happy how accurate it was with just a small 2hz when powered on which could be the capacitor tolerance.

What also is pretty cool is I can move the sensor away from the coil and physically measure the signal drop off. Surprisingly the signal will drop off pretty sharp. This is doesn't necessarily tell you how deep a detector will report an object it senses, just how far the coil goes.

On my Multi Kruzer it showed the Superfly coil being a little out of frequency as the frequency was high which means I probably have a bad connection in the cable. The other coils tested fine and between 5,14, and 19khz there was little difference in range.

On the Tejon I tested stock coil that came in spot on 17.5khz but the Cors Shrew came in at 16khz not that it matters that much on that machine.

Apex was interesting. The Ultimate 9" was 12" and the Reaper 10x14 coil was 14", only 2" more. Now between frequencies and modes. The 20khz was the most followed by MF and MF and range dropped down as frequency was dropped in single freq modes.

If I get my hands on a Nox and Legend would like to test those just for kicks.

Anyways whole purpose was to make a little test device so I can keep working on my coils and test coils that maybe faulty. Just enjoying other aspects of the hobby. Enjoy!

[Cascade Steven]

kac - thanks for sharing.  do you have a link for the schematic?

[Valens Legacy]

Nice project and will be useful for some of us on here, thanks for sharing.

[F350Platinum]

Should be great to see what you do with it. As usual, genius. ?

[Mark Gillespie]

Really nice job.

[Rick N. MI]

Great job! Nice you can test your coils.

[Joe D.]

   That is awsome! What a great little device! When are they gonna be for sale!! "Ken's Coil Frequently Tester" another great tool from KenCo! Made in USA!??

   Now, if you quit throwing them like a Frisbee, they won't keep breaking!???

[GB_Amateur]

I may be missing something, but don't you still need an oscilloscope (or spectrum analyzer) with Fourier Transform readout to conclude what frequency(ies) is(are) being transmitted?

[kac]

Yes you need a scope.

Here is the circuit and pdf to etch. Single sided copper on bottom.

 

 

 

Freq Sensor.pdf