Sigma Metalytics
Also: Sigma device, Sigma tester, Conductivity tester
Sigma Metalytics is a range of handheld instruments that gauge the resistivity of precious metals through electromagnetic induction, dependably flagging fakes.
Sigma Metalytics is a US manufacturer of portable instruments that verify precious-metal coins and bars without damaging them. At the heart of each device lies electromagnetic induction: a coil throws out a high-frequency alternating field, that field passes into the sample, and the instrument reads back the metal's electrical conductivity and permeability. Those readings are then checked against stored reference figures for gold, silver, platinum and palladium.
How It Works and Which Models Exist
The whole approach hinges on how far the electromagnetic field sinks into the metal (the skin effect): turn the frequency up or down and the field reaches shallower or deeper. That variable depth is what lets the tester unmask plated fakes, where a thin skin of real metal hides a cheaper interior — the notorious tungsten counterfeit, for instance, in which a tungsten core wears a gold coat.
The Sigma Metalytics catalogue centres on two families of device:
| Model | Target group | Feature |
|---|---|---|
| Precious Metal Verifier (PMV) | Dealers, private investors | Compact, several probes for different coin thicknesses |
| Professional Series | Commercial testers | Extended frequency range, higher measurement accuracy |
Probes are sized to fit the diameters and thicknesses of the usual coins (1 oz pieces such as the Krugerrand or Maple Leaf, for example). Grab the wrong probe and you may well get a false reading.
What It Does Well — and Where It Struggles
Why it beats simpler checks:
- Leaves the item unharmed and uses no chemicals (in contrast to the acid test)
- Delivers a result in seconds, even while the coin stays in its capsule
- Catches tungsten cores that a magnet test or a density measurement might let slip past
Where it hits its limits:
- The coin has to be tested loose or inside only a thin capsule
- A very thick precious-metal coating can stop the EM field reaching far enough into the core — a forgery wrapped in an unusually heavy gold jacket may skew the reading
- It is no stand-in for X-ray fluorescence analysis (XRF) when a full material breakdown is needed
- The instrument needs recalibrating on a regular basis
For a watertight check, pair the Sigma reading with weight and dimension controls (our Coin Weight Checker and Coin Size Checker handle those), and bring in a professional XRF analysis where the stakes demand it.
In Brief
When the goal is to expose tungsten-core fakes and platings fast and chemical-free, a Sigma Metalytics device is the natural first pick. For absolute certainty on sizeable holdings, though, stacking several test methods together remains the gold standard.