Thickness gauges with bill detector

 

— availability in the device of the built-in detector for check of bills. Such a detector is usually in the form of a UV LED; its action is based on the fact that many modern bills use protective elements that glow under ultraviolet light. There are other, more specific ways to use such a detector — for example, searching for leaks in air conditioners and refrigerators (many freons also have additives that glow in the ultraviolet).