chance pi build

[bernte_one]

thanks dan for the feedback
i made a flat spiral pcb coil last days and will try this first
another think is a small basket coil
with the brn pi and the basket coil (nearly A4 format) i am able to detect a nugget from 0,39gram in a few inches, was also able to detect the 0,39gram nugget with a 18cm monoloop coil with baracuda
but the 45mg nugget is a hard task

if i have no succes with my present pi detectors the chance will get a new chance from me (with the first a had no luck)

[baum7154]

how do the Chance pi perform on small Gold Nuggets

i have a Nugget of 45mg can this be detected by the Chance pi?

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1 gram = 15.432 grains so your 45 mg nugget is 0.6944 grains a very small target! An unmodified Chance even with a good fast coil won't be able to see this. With a 2 stage amp and a 4" fast coil it might see it. With my modified Chance and the 4"X12.5" oval the detector sees a 0.95 grain flake of gold in a vial with a few other much smaller flakes. See post #201 in the Chance PI Coil thread of the coils forum for details on this.

Hope this helps,

Dan

[bernte_one]

how do the Chance pi perform on small Gold Nuggets

i have a Nugget of 45mg can this be detected by the Chance pi?

[baum7154]

After thinking about the discrimination, I prefer the VDI indicating GOLD on targets that may be only partially gold in content. If it indicated IRON then not is it incorrect but I might choose not to dig it up. A GOLD target indication should always be dug up.

Regards,

Dan

[baum7154]

I know it has less gold than most placer nuggets. Does anyone have a PI detector discriminated bench mark for 14kt or 10kt gold? If so does it register as gold or some other metal? Input from a MineLabs PI owner would be good too.

Thanks,

Dan

[golfnut]

The phase may be a ways off for 14K versus pure nugget?

14K is 42% other metals.

[Chet]

Hi Dan

Thank you for the additional information, it all helps.
Chet

[baum7154]

[QUOTE=Chet;200950]Hi baum7154

I sure like the results you are getting. I wish I knew how the Chance PI software worked. green has been charting the response curves of a lot of targets. Another question to resolve is whether an open gold ring has a response curve that is similar to a solid gold nugget without a hole. The key is may be how the Chance PI software is processing small amplitude flat targets versus high amplitude targets.

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I have said in other forums that I don't like to use any targets that form a ring or even a cup because their geometry sets up strong eddy currents that make them even easier to detect than just a blob of the same mass. That said I used my big, old, bulky gold class ring because it is the largest chunk of gold I could lay hands on to test if the discrimination ID'd it as IRON or GOLD. At only 1 division of signal strength, did it ever ID the ring as IRON for very infrequent and short excursions to the right end of the scale. More than 95% of the time at 1 division of signal strength it ID'd as GOLD. I was careful to include a test with the bulky top of the ring where the stone is mounted presented to the coil thinking that at least this helps minimize the effect of the ring geometry. I was surprised that the discrimination was so solid. I don't know how the DISC is derived in software either.

I have been following Greens testing on various targets and wish he had access to some really large nuggets. It would be interesting. In my own testing of small gold and some aluminum small gold simulants (see post 254 above)it appears that there is very close correlation of a 4.5 grain 14 kt gold and a 1/8" diameter/0.7 grain aluminum slug. This slug I calculated to emulate a 5 grain gold nugget based upon the ratios of the specific gravities of aluminum and gold, yielding a compact target of the same volume as a 5 grain nugget. Detection distance with the CHANCE PI is virtually identical for the 14 kt 4.5 grain gold VS the .7 grain AL slug. I believe this method gives credible simulation of small gold.

Thanks Chet,

Dan

[6666]

Thanks Dan.

[baum7154]

Dan
Have you ever taken a photo of the signal at the output of the preamp before it goes into the A-D ?

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Take a look at the second photo in post 162 of this thread. It is what is sent to the A/D.

Regards,

Dan

[6666]

Dan
Have you ever taken a photo of the signal at the output of the preamp before it goes into the A-D ?

[Chet]

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I'm trying to get a better handle on the discrimination of the CHANCE PI on LARGE gold targets and how they are indicated on the VDI at low signal levels. Toward that end I tested a 10kt gold 200 grain ring (approximately 13 grams) using my newest 4" X 12.5" oval coil. It consistently detects the ring flat face to the coil at 11.5" for first detection and at 10" for a solid tone. In an "edge on" attitude to the coil the first detection distance is 10.5" and for solid tone it is 9". Most importantly the VDI consistently shows the target to be GOLD at only 2 units of signal strength in both target attitudes. While this is only an air test it does give me a bit more confidence that large gold nuggets will be properly indicated as GOLD on the VDI and NOT as IRON as we may have feared due to the longer T/C of big gold.

Regards,

Dan

Hi baum7154

I sure like the results you are getting. I wish I knew how the Chance PI software worked. green has been charting the response curves of a lot of targets. Another question to resolve is whether an open gold ring has a response curve that is similar to a solid gold nugget without a hole. The key is may be how the Chance PI software is processing small amplitude flat targets versus high amplitude targets.

Thank you,
Chet

[baum7154]

Hi Dan

Thank you for running the test and the good explanation. 128 grains at 9" is really good. It will be interesting to hear more results from your friends nuggets. Especially if he has any really large ones.

Thank you,

Chet

--------------------------------------------------------

I'm trying to get a better handle on the discrimination of the CHANCE PI on LARGE gold targets and how they are indicated on the VDI at low signal levels. Toward that end I tested a 10kt gold 200 grain ring (approximately 13 grams) using my newest 4" X 12.5" oval coil. It consistently detects the ring flat face to the coil at 11.5" for first detection and at 10" for a solid tone. In an "edge on" attitude to the coil the first detection distance is 10.5" and for solid tone it is 9". Most importantly the VDI consistently shows the target to be GOLD at only 2 units of signal strength in both target attitudes. While this is only an air test it does give me a bit more confidence that large gold nuggets will be properly indicated as GOLD on the VDI and NOT as IRON as we may have feared due to the longer T/C of big gold.

Regards,

Dan

[bernte_one]

thanks for the link

[kt315]

at a site of Andy http://fandy.hut2.ru/ChanceM_121.zip
hex version 1.2.1. it is LAST