Major problems with my new Presidium Multi Tester III...


May 1, 2011
I just bought a brand new Presidium Multi Tester III Diamond/Moissanite tester so I could test for diamonds on my jewelry collection. I was told it was top of the line and the best I could buy. It's been a nightmare.

Even on pieces I know are real diamonds, it gives inconsistent results. Sometimes it doesn't give a result, sometimes it says it's a real diamond, and other times it claims moissanite. On the same rock. I have a 3-diamond pendant. It usually claims the big one is real (occasionally stating it's moissanite) and that the medium and small diamonds are moissanite (occasionally giving real diamond results on the medium one). On a gold ring with two tiny diamonds, it detects the left one as real and the right one as moissanite. It particularly seems to have issues detecting small diamonds.

I've tried making sure the stones were clean, cool, held properly, etc... I've done these tests from a cold start up on the tester, or when it's been warmed up for a little bit. I make sure it touches the diamonds dead-center. Nothing seems to make a difference.

Are these problems normal with this tester? Is there something I'm doing wrong? What exact procedure should I follow when doing these tests?

With inconsistent results, the device is useless... Any help or advice is appreciated.

Thank you.


Sep 3, 2000
I own three of these units and find them 100% on target, so it is likely how you are using it. Number 1, try fresh batteries. Make sure you place your thumb on one side and your forefinger on the other side on the metal plates on the sides of the tester. It really won't test Moissanite, or buzz for metal contact, without your fingers on those metal plates. Also, push the test needle down vertically, perpendicular to the table, all the way into the device. It is spring loaded and depends on a high pressure contact point. I have seen these fail when used on an angle to the table or not pushed down solidly.

Of course, it could be out of calibration through no fault of your own. I imagine there is a warranty period and getting a new one might be the only way to get things right. Hope this is helpful advice.
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