any metal detector users out there?

[Jarrod]

hi everyone,

this is about as unrelated to astronomy as a question can get:

ive got a problem with my metal detector (Garrett ADS grondhog) and im hoping someone here knows something about them. the problem is that its not very sensitive, it wont detect any metal more then 5 or 6cm away, and small items like copper coins have to be within 1cm of the coil before the dial even twitches. these metal detectors are meant to be capable of detecting metal several feet under ground. ive also noticed the 'ground cancel' knob is broken, or at least not working proberly, but i dont know if this is related.

does anyone out there know anything about the inner workings of these machines?

thanks, jarrod.

[ballaratdragons (Ken)]

Hi Jarrod,

It is a myth that Metal detectors can detect metals several feet down. At best, a very good metal detector can detect at 12" at most. And sideways is even worse. Anything more than a few inches outside the coil diameter will be completely missed.

Also, they find it hard to detect objects that are vertical in the ground. Horizontal objects will bounce back a better signal.

[duncan]

Hi Jarrod,
With the groundhog you should be able to pick up pennies or shillings down at least 6". Keep the coil as close to the ground as possible (eg. an inch off the ground or less).
Next , that ground balance knob definitely needs to be fixed. It's job is to balance the machine to the ground in highly mineralised dirt. If it is adjusted to far then performance capability suffers. I have quite a collection of old coins that i found when i owned a "Whites 6000D Series 2".
Hope this helps. When adjusting for balance you should just be able to detect a slight hum type noise. This same sort of noise should get louder over a target.
Cheers,
Duncan

[Jarrod]

i opened up the detector to have a look at the ground cancel knob. it takes ten turns to get from 'off' to 'on', according to the instruction manual. it seems that the moving parts have worn down, so the knob feels strange to turn, but still should work ok. but because the detector is not sensitive enough to detect ground minerals, i cant test the ground cancel.

[Outbackmanyep]

Im guessing you're using fresh batteries!?
Im used to the XT17000 (auto ground tracking! YAY!) so i wouldn't know off-hand, but have you tried contacting Jack Lange Detectors at Heddon Greta?? Maybe a Garrett dealer might be able to check it over and make sure its nothing inside thats giving you trouble or the coil leads etc....

Hope this helps!