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Nokta FORS Calibration?


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My nokta fors gold lost display info,and is showing only system info, (p.p.toggle switch is sticky)so I was out detecting yesterday with my well used (dare i say slightly abused) gmt. I think it was a bad day for solar radiation/geo-magnetic yesterday, but it got me to wondering how do i test for this (need of cal.)at home?

I would assume the test patch is handy for testing the consitency of readings and sensitivity, but short of another machine of same model how do you guys determine if it needs it, and what does it cost?

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Cost of a "tune up" would simply depend on the manufacturer. In many cases postage costs may be the majority of the cost.

As a rule my detectors either work or they do not. In 40 years and countless detectors I only ever sent one in once to get "tuned up". The odds are pretty low of a detector needing this.

If a detector is consistently causing you to think something may be wrong with it, then sending it in to get checked out might be a way to set doubts aside. Most of the modern digital type detectors have very little that can be calibrated, but many older analog designs have numerous internal settings that can be adjusted and that may therefore be out of adjustment. I do not think the GMT is a detector that has any history of calibration issues. Other detectors, like the Fisher CZ series, are kind of famous for it. Tom Dankowski has a little sideline business testing and calibrating Fisher CZ detectors for people.

Analog models were often tuned at the factory for the particular coil they shipped with. The one I sent in was a Fisher Gold Bug 2. I got a different coil for it (a smaller one), and sent it in to get the detector specifically tuned for use with that coil. Most Tesoro detectors out there are tuned for the coil they ship with, and making another coil the primary use coil would be a reason to consider getting it retuned.

Keep in mind also that when detectors do end up misbehaving, in the vast majority of cases it is a coil and cable issue, not the control box, that is causing the problem.

Long story short I wish I had a better answer. It is pretty obvious when a detector goes truly haywire. Determining if a detector is just a bit off is a whole different problem. You could compare air tests on a nickel or dime with other people on the Internet, but frankly that would probably be frustrating also. People interpret what a signal is at fringe distances with considerable variation. I tend to be conservative and note clean, solid, repeatable signals as being what I would quote. Others note the faintest hint of a whisper of a signal as their number. The difference between what I would quote and somebody else would quote air testing the same machine could be measured in inches.

All I have ever done with my detectors is just wave something under the coil. If it goes beep, I go detecting. It is entirely possible I have owned detectors that were consistently one inch shy of where they should have been and never knew it. It no doubt does happen with machines that are out there, but unless a person has access to a second identical machine it would be very hard to know.

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As alway, a prompt and informative post Steve. Thank you.

The machine just seemed noisy and inconsistent during multiple swings over target and harder to adjust, no ground tracking was in use.

I also had left my cell phone in my pocket on my detector side, could it cause interference?

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