Technical
XRF gold testing explained: how it works, how accurate it is, and which analyzer to buy
Non-destructive, under a minute, a fraction of a percent. What those figures actually mean, where XRF belongs on the floor, and how to choose between the two Signet benchtop analyzers.
· 8 min read · By Dhyey Mehta
XRF gold testing tells you what a piece is actually made of, in under a minute, without destroying it. This guide explains how the method works, what the published accuracy figures mean, where testing belongs in a factory, and how to choose between the analyzers we supply.
Every figure is the catalogue figure already on the gold testing and XRF page. Where the catalogue is silent, this article is too.
How X-ray fluorescence works
Every element has a signature. When a sample is excited by X-rays, each element in it emits X-rays of its own at characteristic energies — gold at one set, silver at another, copper at a third. An XRF analyzer fires a controlled beam at the sample, its detector reads the spectrum that comes back, and the software converts the peaks into a composition.
Two things follow from that. First, the piece is not touched beyond the beam, which is why the method is called non-destructive. Second, the quality of the answer depends on the detector: its resolution decides how cleanly it separates neighbouring peaks, and that is the main specification that separates the two Signet models.
What the published numbers mean
| Parameter | Signet FSDD | Signet Si-Pin |
|---|---|---|
| Detector | Silicon PIN | SIPIN (USA) |
| Resolution | 145 ± 15 eV | 165 ± 5 eV |
| Analysis range | 1%–99.99% Au | ppm to 99.99% |
| Accuracy | ±0.10% on gold content | ±0.03% (Au ≥ 99.9%) |
| Sample form | Solid, powder, liquid | Solid, powder, liquid |
| Elements | Up to 72 kinds | No. 11 to No. 92, excluding light elements |
| Test time | 10–60 s; ~40 s for best results | Approx. 5–60 s |
| Sample chamber | 368 × 298 × 86 mm | 300 × 300 × 100 mm |
| Net weight | Approx. 40 kg | Approx. 25 kg |
Resolution
Stated in electron-volts, and lower is better: it is the width of the peak the detector draws for one energy. At 145 ± 15 eV the FSDD separates adjacent elements more cleanly than the Si-Pin at 165 ± 5 eV. For pure gold verification the difference is small; for alloy work with several elements close together it is the reason to prefer the FSDD.
Analysis range and accuracy
The FSDD is specified from 1% to 99.99% gold; the Si-Pin from ppm upwards, which is what makes it the trace-element instrument. The FSDD holds gold content to ±0.10%. The Si-Pin is specified at ±0.03%, and that figure is stated for gold at 99.9% and above - read the qualifier, not just the number.
Test time
Faster is not automatically better. The FSDD entry specifies a 10 to 60 second window and roughly 40 seconds for best results; a shorter test trades certainty for speed. Set the time to the decision you are making: a counter check and a refinery settlement are different questions.
Where testing belongs in a factory
XRF sits at stage ten of the workflow, measuring instruments, but a manufacturer uses it at three points:
- Incoming verification. Scrap, bullion and returned goods are tested before they enter the melt. This is where a benchtop unit pays for itself first.
- In-process control. Checking a melt before casting catches an alloy error while it is still one crucible rather than a whole tree.
- Outgoing assurance. Finished pieces are verified before they leave the floor, and before hallmarking. In India the hallmarking scheme is administered by the Bureau of Indian Standards; XRF is how a factory knows what it is sending for assay.
For a retailer or buyer the use is simpler: settling a purity question at the counter in under a minute, without marking the piece.
The environment the instrument needs
The FSDD is specified for 0–35 °C ambient temperature, humidity below 70%, and a 230V/50Hz input. Keep either benchtop unit out of direct heat and away from polishing dust — the same dust that damages setting machines settles in an analyzer's chamber. The portable gold tester is an electronic karat tester rather than an XRF analyzer, and it runs on a rechargeable battery, so it needs no power point where it is used.
Choosing between the Signet models
| If this is you… | Start with |
|---|---|
| Primarily high-purity gold verification, wide element coverage | Signet FSDD |
| Trace detection down to ppm, or a lighter 25 kg unit | Signet Si-Pin |
| A karat reading away from the bench | Portable gold tester |
| Comparing the whole family | Ask for the Signet-PC datasheet |
The Signet-PC is listed in the catalogue alongside the other two without a published parameter table, so we do not compare it here. We send the current datasheet on request rather than have you infer its figures from the FSDD and Si-Pin.
What we do not publish
Prices, calibration intervals, certification and warranty terms for the analyzers are not in our catalogue and are confirmed in writing on your quotation. Some Signet values are printed small in the catalogue; for procurement, treat the manufacturer datasheet as authoritative.
Compare the analyzers, or tell us what you test, how often and where — send an enquiry or call +91 98216 12340.
Answers
Related questions
How does XRF gold testing work?
The analyzer excites the sample with X-rays; each element in it responds by emitting X-rays at its own characteristic energy. The detector reads that spectrum and the software converts it into a composition — how much gold, silver, copper and so on the sample contains. Nothing is cut, scraped or dissolved, which is why XRF is called non-destructive.
How accurate is XRF gold testing?
The Signet FSDD holds gold content to ±0.10%, analysing from 1% to 99.99% gold. The Signet Si-Pin is catalogue-specified at ±0.03% for gold at 99.9% and above, and analyses from ppm to 99.99%. For best results the FSDD entry specifies roughly a 40-second test within a 10 to 60 second range.
Does XRF testing damage jewellery?
No. The piece sits in the sample chamber and is analysed without contact beyond the X-ray beam. That is why it suits finished jewellery, incoming scrap, powder, liquid and customer walk-ins equally; both benchtop Signet models are specified for solid, powder and liquid samples.
Which XRF analyzer should I buy, the Signet FSDD or the Si-Pin?
If your work is primarily high-purity gold verification, the FSDD's 145 ± 15 eV resolution and 72-element coverage is the stronger instrument. If you need trace detection down to ppm, or want a lighter 25 kg unit with a smaller footprint, the Si-Pin fits better. Tell us your sample types and volumes and we will recommend one.
Can I use a portable gold tester instead of a benchtop XRF?
For a karat reading away from the bench, yes. The portable gold tester is an electronic tester rather than an XRF analyzer: a pen probe reads the metal on a test pad and the screen shows the karat, 0 to 24K, on battery power. It does not list the other metals in the alloy, which is what a benchtop Signet is for.