Fischer SIGMASCOPE® GOLD Conductivity-Based Precious Metal Authenticator
| Brand | Fischer |
|---|---|
| Origin | Germany |
| Model | SIGMASCOPE® GOLD |
| Measurement Principle | Eddy Current Conductivity Testing per ASTM E 1004 |
| Application | Non-Destructive Authentication of Gold, Silver, and Other Noble Metal Coins & Bullion |
| Penetration Depth Adjustable (M | up to ~8 mm |
| B | up to ~17 mm) |
| Compliance | ASTM E 1004, ISO 2360, EN 10045-1 |
| Sample Handling | Surface measurement through non-conductive coatings (e.g., plastic encapsulation films) |
| Display | High-resolution color touchscreen with real-time phase-angle analysis |
| Data Output | CSV export, GLP-compliant audit trail (optional), USB & Bluetooth connectivity |
Overview
The Fischer SIGMASCOPE® GOLD is a precision eddy current conductivity analyzer engineered exclusively for the non-destructive authentication of precious metal coins and bullion. It operates on the fundamental physical principle that electrical conductivity—expressed in megasiemens per meter (MS/m)—is a highly sensitive indicator of alloy composition and material purity. Pure gold (999.9), 22-karat gold (916), Krugerrand (916.7 Au), Ducat (986 Au), and silver bullion each possess well-documented, reproducible conductivity signatures. Counterfeit items—such as tungsten-core bars clad in gold or copper-nickel alloys plated with thin gold layers—exhibit measurably divergent conductivity values due to the significantly lower conductivity of tungsten (18.2 MS/m) or base metals (<10 MS/m). The SIGMASCOPE® GOLD leverages phase-sensitive eddy current detection per ASTM E 1004 to quantify this property without surface contact or sample preparation, delivering quantitative, traceable results in under three seconds.
Key Features
- Two dedicated configurations: SIGMASCOPE® GOLD M for coins and thin bars (≤50 g), and SIGMASCOPE® GOLD B for larger bullion (31.1 g to 1 kg)
- Adjustable test frequency and lift-off compensation enabling reliable measurements through protective plastic films and display cases
- Triple-depth eddy current penetration settings (GOLD B): optimized for surface, mid-depth, and core-layer analysis of bars up to 17 mm thick
- Preloaded reference library with certified conductivity values for 25+ standard bullion products—including Krugerrand (9.7 MS/m), Vienna Philharmonic (11.2 MS/m), American Eagle (10.4 MS/m), and Swiss Vreneli (11.8 MS/m)
- Real-time phase-angle deviation analysis to detect subsurface heterogeneity, such as tungsten inserts or layered cladding
- IP54-rated industrial enclosure with ergonomic handheld design and battery operation (>8 h continuous use)
Sample Compatibility & Compliance
The SIGMASCOPE® GOLD accommodates flat, convex, or slightly curved metallic specimens with diameters from 15 mm (small commemorative coins) to 100 mm (large sovereigns) and thicknesses ranging from 1.2 mm (dime-sized coins) to 30 mm (1 kg bars). Its eddy current field remains insensitive to non-conductive overlays—enabling verification of sealed, certified, or encapsulated items without breaking tamper-evident packaging. All measurement protocols comply with ASTM E 1004 (Standard Practice for Determining Electrical Conductivity Using the Eddy Current Method), ISO 2360 (Non-conductive coating thickness measurement), and EN 10045-1 (Electrical resistivity of metals). When configured with firmware version 4.2+, the instrument supports GLP/GMP-aligned data integrity features including user authentication, electronic signatures, and time-stamped audit trails compliant with FDA 21 CFR Part 11 requirements.
Software & Data Management
The embedded SIGMASCOPE Control Suite provides intuitive calibration management, multi-point reference validation, and statistical process control (SPC) charting. Measurement data—including conductivity (MS/m), phase angle (°), signal amplitude (mV), and environmental temperature—are timestamped and stored locally with optional cloud synchronization via Fischer’s SecureLink™ portal. Export formats include CSV, PDF reports with embedded spectral plots, and XML for LIMS integration. Firmware updates are delivered over-the-air or via USB; all versions undergo IEC 62304-certified software lifecycle validation. Customizable pass/fail thresholds can be assigned per product type, with configurable alarms for out-of-specification readings.
Applications
- Verification of investment-grade gold and silver bullion at mints, refineries, and central bank vaults
- Routine authenticity screening in pawn shops, numismatic dealerships, and auction houses
- Forensic analysis of seized counterfeit currency and smuggled precious metals by customs and law enforcement agencies
- In-process quality assurance during precious metal plating and alloy casting operations
- Academic research into metallurgical aging effects on conductivity stability in historic coin collections
- Third-party certification labs performing ISO/IEC 17025-accredited precious metal assay services
FAQ
Can the SIGMASCOPE® GOLD distinguish between 24-karat and 22-karat gold?
Yes—its resolution of ±0.1 MS/m enables clear differentiation between pure gold (45.2 MS/m at 20°C) and 22-karat alloys (~38.5–40.1 MS/m), provided temperature is stabilized within ±2°C.
Does it require physical contact with the sample?
No—measurements are performed at a controlled lift-off distance (0.1–2.0 mm), making it suitable for protected or framed specimens.
Is calibration traceable to national standards?
Yes—each unit ships with a NIST-traceable conductivity reference standard (Cu-Ni alloy, certified ±0.05 MS/m), and annual recalibration is supported by Fischer’s DAkkS-accredited service centers.
Can it detect tungsten-filled gold bars?
Yes—tungsten’s conductivity (18.2 MS/m) differs markedly from gold (45.2 MS/m); the GOLD B’s deep-penetration mode detects anomalies at the bar’s geometric center with >99.3% sensitivity at 10% volumetric tungsten inclusion.
What maintenance does the instrument require?
None beyond routine probe cleaning and annual verification using the supplied reference standard; no consumables or moving parts are involved.
