A "trick" has been going on around here for awhile now. Periodically my ATM
card won't register on the "swiper" and the clerk will put it inside a
plastic bag. When the plastic is pulled taut and the card is run through
again, the magnetic stripe is read successfully.
What Is The Physics In This (WITPIT?), as I like to ask my student?
My guess is that the plastic bag's thickness moves the card away from the
magnetic pickup head on the "swiper" which is just enough to make the
sensitive zone of the head's sensing gap just a tiny bit smaller, thus
perhaps overcoming some smearing of the magnetically encoded data. I've
always had this happen when people were in line behind me so I have never had
the chance to try keeping the bag still and moving just the card.
I've also seen people try, sometimes with success, to "polish" the stripe on a
shirt or blouse. I suppose that could remove loose ferrite particles or dirt.
Has anyone looked into this phenomenon or is this a matter of synchonicity?
Jim
--
James R. Frysinger
Lifetime Certified Advanced Metrication Specialist
Senior Member, IEEE
Office:
Physics Lab Manager, Lecturer
Dept. of Physics and Astronomy
University/College of Charleston
66 George Street
Charleston, SC 29424
843.953.7644 (phone)
843.953.4824 (FAX)