Handheld metal detectors can pick up signals from the magnetic ink on U.S. cash, a new study found.
Think those TSA agents waving a metal-detecting wand at your pockets only know how many coins you're carrying? Think again.
Metal detectors can tell how much cash is on you, too, according to a new study by researchers at the University of Washington's Applied Physics Laboratory in Seattle, the Daily Mail reported.
The handheld metal detectors get signals from the magnetic ink dollar bills are printed with, and the strength of the magnetic signals increases when bills are stacked together.
In other words, don't try smuggling big stacks of cash through airport security.
The discovery by Antao Chen and Chris Fuller, which they're presenting at is still in its nascent stages, though, and the pair says there's still no way for the metal detectors to count the exact amount of cash they find. They can only count the number of bills they find.
That's because a dollar bill carries the same amount of responsive magnetic ink as a $100 bill — meaning somebody carrying $10 in ones would trigger the metal detector just as much as somebody carrying $1,000 in hundreds.
Other sources can interfere with the signal, too, particularly ones that also have magnetic ink, New Scientist noted. Adding other equipment to the simple detectors could cut down on that interference, one scientist at the University of Cambridge in the United Kingdom said.