How does a counterfeit detector work?

Counterfeit detectors are useful additions to an Epos system, allowing to spot counterfeited banknotes easily, sometimes even before the customer can know you are checking.

Three technologies can be used:

- UV bank note checker: this type of counterfeit detector uses UV lamps to shed ultraviolet light onto the banknotes to reveal banknote embedded safety features such as UV marks, metal thread or watermarks. UV marks will glow when exposed to UV light, metal threads will shine out, and watermarks will be fully visible. If any of these security features fail to appear, or seems blurred, the user will see the banknote may be a counterfeited one.

- Note checker pens: using an iodine solution, these pens are used to mark the banknote. The ink does not react when it is applied onto legitimate banknotes made of fibre-based paper, and the intended pen colour shows; but using the pen on a banknote made of normal copy paper will leave a dark stain. This very inexpensive counterfeit detector therefore does not work on the few but possible occasions when a counterfeited banknote is made of actual fibre-based paper. Also, these counterfeit detectors will not work on plastic, polymer banknotes widely used in Asia-Pacific countries, and sometimes used in the UK.

- Automatic counterfeited banknote detectors: these machines double-up as banknote counters. Large wads of notes are inserted, and the built-in image sensors count the notes, calculate the total amount which is shown on the device’s display, and detect counterfeited notes. Some models are certified by the Bank of England to have a 100% accuracy.