Algoforce And Coil Calibration Errors

[phrunt]

The new V2 firmware for the Algoforce included a change around coil calibration, in past versions an out of spec coil would fail calibration, basically saying the coil needs calibrated, usually for ultra fine mode however you could still manually select and use ultra fine mode for detecting, albeit sub optimally and you would likely be better off using it in fine mode where it did calibrate for best results.

Since V2 the modes that don't calibrate have been blocked from use and you can no longer select them on an out of spec coil, this has bought to light just how many out of spec coils are floating around out there.  Common offenders are the older Detech coils, especially the smaller coils and the two Nugget Finder Sadie coils, the original and the Mk2, I've noticed a number of people with the Sadies and the problem and the Nugget Finder 12x8" EVO is also hit and miss although I'm sure there are more.   I would assume this is something to do with being hand wound coils and just not getting it perfectly right every single time.  With the Detech coils they're generally really old coils people are using and I'm not sure if that's something to do with it, coils going out of spec over time or just out of spec from the start? 

All of this went unnoticed on the earlier GPX series.

Some people have been upset that in the older firmware they were using ultra fine with their coil and now they can't with the new firmware, the idea of blocking out the out of spec coils from using modes they don't calibrate in was because they were not going to work properly in that mode so using ultra fine with a coil that won't calibrate is more like a placebo, it makes you feel good you're in ultra fine but you're not benefitting from doing so.

The coil calibration algorithm in the v2 firmware is the exact same as in the previous firmware so both would have the same results with pass/fail on coils, the only difference being version 2 blocks the sub optimal coils using the modes they won't work well in. 

Here are some examples of the discussion around it the past couple of days with people having these problems.

One person thinks their Sadie MK2 is a Coiltek coil, mistake on their part there.

The good news is it looks like Nugget Finder or at least the dealer replaced the out of spec MK2 Sadie for a customer and he got a working replacement, this seems the best path forward on coils that are under warranty still if the dealers/manufacturer will replace them, I'm sure Coiltek will if the problem pops up for their coils as they advertise them for the Algoforce although I've never seen one of their coils having the problem.

Where the guy in the original post says his ground balance numbers disappear, this behaviour is normal he's just only new to the detector, after 3 seconds the ground balance numbers do go away after performing a ground balance.

[Jeff McClendon]

That was my experience with a Detech 11X6” coil. It wouldn’t calibrate in Ultra Fine with the previous software but I could still use it in Fine, etc. With v2 it wouldn’t calibrate in Ultra or Fine. It wasn’t that old. That coil went bye, bye. 
 

I have an ancient Nugget Finder Advantage 10X5” coil that calibrates easily. 
 

Got a new 9” Coiltek Elite Max for a ridiculous price ($320 US). It calibrates, no problem. 

[phrunt]

Yea, if a coil doesn't calibrate in ultra fine I wouldn't use it personally as I only use ultra fine however, I'd be pretty annoyed if I bought a new coil and it didn't calibrate in ultra fine when other people with the exact same coil can calibrate in ultra fine.

Nugget Finder and Detech seem the two problematic brands with inconsistencies in manufacturing but my 14x9" EVO and my Sadie both calibrate in ultra fine.  I don't have any Detech GPX coils anymore, I gave mine away some time ago as I never used the particular size which was a 15x8" bundle wound mono, too insensitive for me.

[Aureous]

I have a Sadie 8x6 that initially didn't calibrate (multiple occasions) and I put it aside many months ago. Whilst doing all the prototype testing recently, I put it back on to do a comparison and voila....it calibrates now? A real head scratcher....

[phrunt]

Just now, Aureous said:

I have a Sadie 8x6 that initially didn't calibrate (multiple occasions) and I put it aside many months ago. Whilst doing all the prototype testing recently, I put it back on to do a comparison and voila....it calibrates now? A real head scratcher....

Does it stay calibrated when in use? Some Sadies calibrate initially but after some use drop back to uncalibrated, this behaviour has been noticed only with MK2's that I'm aware of so far.

[Aureous]

Maybe...thats a good question. Ive only used it for comparison testing in the workshop. Ive got such a plethora of prototype coils now, I dont see the need to use it in the field. Suppose I'll have to now. I hate unanswered questions lol

[GeoBill]

Phrunt, do you think that changes in temperature can effect calibration, i.e. for the Sadie coils that start in but then drop out? Are the Sadie coils epoxy filled?

[phrunt]

3 minutes ago, GeoBill said:

Phrunt, do you think that changes in temperature can effect calibration, i.e. for the Sadie coils that start in but then drop out? Are the Sadie coils epoxy filled?

Well above my pay grade I don't know sorry, I don't think the Sadies are epoxy filled but I've never seen inside one, at least they're not advertised as such and not properly waterproof which normally an epoxy filled coil would be an easier coil to make waterproof.

[Erik Oostra]

On 6/7/2025 at 6:12 AM, Jeff McClendon said:

That was my experience with a Detech 11X6” coil. It wouldn’t calibrate in Ultra Fine with the previous software but I could still use it in Fine, etc. With v2 it wouldn’t calibrate in Ultra or Fine.

My new Detech 11x6 coil calibrated in Ultra Fine with the old software but with this new software it just calibrates in Fine.. Like yours, it's bye bye for mine too.. It's been replaced in the lineup by a rectangular PMC 12x4 coil which calibrates no worries in Ultra Fine.. it also runs better on hot ground and is just as sensitive as the Detech 11x6.. 

All my other coils calibrate in Ultra Fine with the new software.. That's the: rectangular PMC 18x6, 14x9 Evo, 9x9 Elite and 8x6 Sadie Mk II.. Phrunt's got me a bit worried about the Sadie now.. But out bush I'm mainly using the 9x9 or 14x9 coils and for the beach the bombproof PMC 18x6..