Sigma Metalytics
Also: Sigma Device, Sigma Tester, Conductivity Tester
Sigma Metalytics is a product line of handheld testers that measure the specific resistivity of precious metals by electromagnetic induction, reliably exposing counterfeits.
Sigma Metalytics is a US brand that makes handheld devices for the non-destructive authenticity testing of precious-metal coins and bars. The instruments work on the principle of electromagnetic induction: a coil generates a high-frequency alternating field that penetrates the metal under test and measures its electrical conductivity and permeability. The result is compared against stored reference values for gold, silver, platinum and palladium.
Working principle and product variants
The measurement relies on how deep the electromagnetic field penetrates the material (the skin effect): depending on the selected frequency, the field reaches to different depths. This makes it possible to detect clad objects too, where a layer of genuine metal conceals an inferior core — such as the dangerous tungsten forgery, in which tungsten cores are sheathed in gold.
Sigma Metalytics offers two main variants:
| Model | Target users | Notable 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 |
The probes are matched to common coin diameters and thicknesses (for instance 1-oz coins such as the Krugerrand or Maple Leaf). Choosing the wrong probe can lead to false readings.
Strengths and limits
Advantages over simpler methods:
- Non-destructive, no chemicals (unlike the acid test)
- A reading in seconds without removing a coin capsule
- Detects tungsten cores that may slip past the magnet test and density testing
Limitations:
- Coins must be tested unpackaged or in thin capsules
- Very thick precious-metal layers can stop the EM field reaching deep enough into the core — a forgery with an especially heavy gold shell can distort the result
- No substitute for X-ray fluorescence (XRF) for a full material analysis
- The device must be recalibrated regularly
For a complete check, combine the Sigma test with weight and dimension control (use our coin weight checker and coin size checker) and, where needed, a professional XRF analysis.
In brief
Sigma Metalytics devices are the tool of choice when the goal is to expose tungsten-core forgeries and cladding quickly and without chemicals. For final certainty on large positions, combining several testing methods remains the gold standard.