Time Constants of Metallic Targets

[Elliot]

I thought it would be useful to create a centralised place to list approximate time constants for different types of targets, e.g.-

Base Metals, by weight (assuming round spheres):
- Small gold (1 gram)
- Small silver (1 gram)
- Medium sized gold (28 grams = 1 Ounce)
- Medium sized silver (28 grams = 1 Ounce)
- Small copper (1 gram)
- Medium copper (28 grams = 1 Ounce)
- etc.

Coins by Country:
- USA
- Canada
- UK
- Australia
- New Zealand
- etc.

Anyone that can assist to develop this database is welcome to contribute. I know that TC's will fit in ranges, depending upon assumptions (e.g. shape, purity, orientation etc.) . Let's not try to over complicate this too much - it's a staring point.

[Skippy]

It is certainly worth doing this for common readily-obtainable, or readily manufacturable items. Such as coins that are common, or fairly cheap to obtain. And manufactured items could include cast lead objects, targets made from coins, sheet drinks-can aluminium, copper wire/sheet, (or Mr. Greens favourite aluminium kitchen foil !).
But not items like 28 gram spheres of pure 24K gold. ( why 28 grams ? It would be slightly more relevant to use 1 Troy Ounce = 31.1 grams , though I doubt anyone will be wanting to re-cast their nice Swiss ingots). Personally, I would avoid any gold targets other than coins, ditto with silver items.
And items that are very variable, or not reproducible, like real gold nuggets, jewellery, ancient corroded coins are only worth including for 'academic' purposes.

It's worth pointing out time-constants are only accurate for PI machines. VLF's will mis-report some targets due to skin effect, so it's worth us stating how the measurement was made.

Myself and Mr. Green have done a modest amount of experimentation on this subject, we could no doubt add our bit.

[green]

Some US coins. Target TC is faster early in the decay for some targets. Can take 1 to 2 TC's before straight line decay linear X log Y.