How a counterfeit money detector works
Reviewed on 1 September 2026 · By the Detectalia technical team
An automatic detector does not «look» at the note the way a person does: it subjects it to several simultaneous physical analyses that no counterfeit can pass all at once. These are the checks, and what each one contributes.
The checks, one by one
Professional-grade equipment combines up to seven analyses on the same note:
- Infrared ink (IR): parts of a genuine note are printed with inks that are visible — or invisible — only under infrared light, in an exact pattern.
- Ultraviolet ink (UV): fibres and motifs that fluoresce at the right wavelength; ordinary paper and plastics glow differently.
- Magnetic ink (MG): certain areas carry ink with magnetic properties that a sensor reads like a signature.
- Metallic thread (MT): the security thread embedded in the note is detected physically, not by eye.
- Size and thickness: each denomination has precise dimensions and weight; a deviation of tenths of a millimetre gives the note away.
- Colour and image: spectral analysis compares the note against the pattern for its denomination.
Why the combination matters
Forging one of these features is possible; forging all of them at once is, in practice, not. A starch-washed paper fake fools the detector pen, a careful print can fool the eye, and a plastic film can mimic a polymer note's feel — but none of them will reproduce the infrared pattern, the magnetic signature and the exact thickness at the same time. That is why the detector decides on its own: accept or reject, with no interpretation asked of the cashier.
Testing by the European Central Bank
The European Central Bank puts authentication devices through tests with thousands of real counterfeits withdrawn from circulation. Only equipment that rejects them passes, and the list of successful devices is public and continuously updated. It is the seal that guarantees a detector does what it promises — always ask for it before buying. Detectalia detectors pass these tests with 100 % detection, and multi-currency models verify pounds sterling as well as euros.
What about banknote counters with detection?
Professional banknote counters build in the same sensors (UV, MG and IR depending on the model) and verify while they count: a thousand notes a minute, with an alarm and an automatic stop on any suspect note. For businesses cashing up daily, it is the way to combine counting and security in a single pass.
Frequently asked questions
How long does an automatic detector take to verify a note?
Around half a second per note on counter-top devices, in any of the four possible orientations.
Does a detector need maintenance?
Very little: periodic sensor cleaning (dedicated cleaning cards exist) and firmware updates when the manufacturer publishes them.
Does it also check pounds and other currencies?
Multi-currency devices verify several currencies — the D7X, for example, handles pounds sterling, euros and other European currencies. Check the currencies supported by each model on its product page.