Conversely, measurements below a threshold voltage indicate that practically no current flows through the gem, and that the gem therefore may be a diamond—if other tests such as a thermal conductivity test show it to be as one.
At the brain of the gem tester is a microcontroller for processing a multitude of analogue inputs to produce a number of outputs for ensuring whether a measurement for a gem under test is, in fact, within a specific range, signaling that it is moissanite or synthetic diamond.
Getting the feel
Using a diamond tester/moissanite tester/multi-tester is not complicated. A good start is to read its user guide/instruction manual line by line, and make sure you are not doing anything wrong. If your tester works consistently (gives the same reading on the same stone every time) and correctly (accurately identifies stones), then you do not need to know the principle on which it works. However, if you are having problems, then the following basic tips will help solve most problems:
1. The probe of the tester must be clean, especially if it has not been used for some time. Clean it by rubbing it at right angle in a circular motion on a piece of white bond paper.
2. Clean the stone by wiping it with a clean cloth soaked in alcohol. Alcohol works best because it evaporates quickly and leaves no residue.
3. Place the tester probe on the stone at right angle, and press firmly to make good contact (hold the tip at right angle so as to not break it). You should get a result in about three seconds. If not, remove the probe, wait for a few seconds for the stone to cool down and try again.
4. Do not test the same stone repeatedly, until it becomes hot. Hot stones do not register as diamond, even if these are. (Inconsistent readings miraculously become consistent if you wait a minute or two for the stone to cool down.)
Further, relatively-cold stones give a high reaction on the LED indicator segments, and relatively-warm stones give a low and often sluggish reaction. (A very tiny diamond on a hot day may only move one or two LED segments up.)
A multi-tester can show you if the stone is a diamond or not. It carries out the diamond test and then, a fraction of a second later, it carries out the moissanite test. Its microcontroller combines both readings and calculates a response. You will not get correct readings if, in that first split second, you remove and replace the probe or slide it across the stone or press hard, then let go and again press hard. It only works if you put the probe in the centre of the stone firmly once. As with all testers, this is not a problem if you can see what you are doing and you have a steady hand.
An electronic diamond tester with state-of-the-art technology assures quick, accurate readings to determine if a diamond is real or fake. Most multi-testers utilise a combination of the proven thermal and electrical conductivity principles.
The tester probes, together with the electronics circuitries, are designed to pick up and segregate data collected from the stones via a customised microcontroller. Within a split second, the test result is displayed on an electronic display. However, no tester can offer 100 per cent guarantee of identifying all diamonds correctly. There are always exceptions, and these apply to almost all brands of electronic diamond testers.