Margin of Error

[vitreous]

I have been wondering what the typical margin of error, and repeatablity, might be for the sarin type measurements (crown and pavillion). Any ideas?


Thanks,
David

 

[pricescope]

Best accuracy that can be acheived for pavilion angle measurements is ±0.1°. In reality the error can be higher.

Measurement error depends on model (e.g. Diamension or BrillianEye) and diamond part (pavilion angle measurement is more accurate than crown angle).

It also depends on the optics used because diamonds of different size can be measured more accurately if optimal optics for the size is selected.

 

[vitreous]

Thanks leonid,


So is it true that if an AGS cert says a diamond has a crown angle of 34.3 I could actually be outside of an AGS rating of 1A?

But with a pavilion % of 42.6 I am in most cases within 1A?

Am I following a logical line of thought here?

David

 

[rbjd]

I'm glad somebody brought this topic up. Everybody seems to rely on AGS or Sarin results as the absolute truth and then use those numbers for the HCA thinking they are correct.

All the machines, like any scientific equipment, have margins of error. The companies publish the specs. However, the machines can also be out of calibration or improperly calibrated which increases the margin of error.

Having had a diamond independently appraised, I can tell you from experience that the appraiser came up with slightly different numbers than the seller. Even the seller had more than one report with slightly different numbers. It depends on the manufacturer, the machine, the software, and other factors.

The question is whether the numbers are repeatable or whether they all fall into a certain range. AGS numbers are averages and not necessarily accurate for all angles. A properly run complete Sarin is much more enlightening than AGS.

At some point you need to either trust your eyes or an independent appraiser.