Posted on 17th January 2018 in the categories: Magnetics

Credit Cards VS. Magnets: How Does It Work

Credit card mag-strip going through card reader

Purchasing with your card is often a stress-free process, especially with the relatively new contact-less craze. But sometimes there’s a hitch in the process – your card won’t scan. Not to worry, you haven’t overspent during Christmas – it’s a pretty common issue and it can happen to anyone. It just means something’s wrong with your card’s magnetic strip.

How do magnets work in credit cards?

It’s simple; all debit and credit cards have a black strip on the back containing little magnets arranged in certain configurations to relay information, also known as the ‘magstrip’. This magnetic strip, contains everything from your name – to your bank account number – to your limits. Basically, all the information your bank or a retailer would need to know about you to complete a transaction.

The tiny iron-based particles that make up the strip can be magnetised in different directions by a device that produces a strong magnetic field. This device is a ‘solenoid’, or more simply; a coil wound into a tightly packed helix.

Metallic Core Diagram

Wire is wound around a high-permeability, metallic core which produces a strong magnetic field when a current is passed through it. This device encodes the required information onto the magnetic strip, which is then pasted on a plastic card.

Can magnets erase the information on credit cards?

Yes, magnets can tamper with the magnetic strip on credit cards, erasing the information stored there and rendering them useless.

With magnetic strips on everything from MasterCards to loyalty cards, and magnets built into many everyday objects, demagnetization can be an accident just waiting to happen. “There are some environments where it’s fairly easy to demagnetize a card,” says Kevin Rhoads, a research engineer at Dartmouth University in New Hampshire.

Why did this happen?

It is important to note that it’s not the strength of the magnet, but the duration of exposure. Professor Sherry explained that even a fridge magnet would have an impact on credit cards after a long enough time.

Prolonged exposure to an external magnet can throw the information out of place, making the card unreadable. “If you disturb the way that the particles were aligned in the first place by putting a magnet close to it, it will disrupt that encoding,” says Steve Mathison, vice president of product and business development for First Data, a payment-processing company.

How to prevent this

It is important to note where trouble lies when it comes to demagnetizing magnets. Below is a list of a few common places to keep in mind:

  1. Refrigerator door magnets – The magnets that keep your fridge door shut are incredibly strong and can wipe your card almost instantly.
  2. MRI machines – MRI machines contain large, powerful magnets which was discussed in an earlier blog.
  3. Purse & wallet magnets – While these magnets don’t appear strong enough to demagnetise a credit card, if the card is placed directly over the magnetic latch then some data may be erased.
  4. Security tag deactivators – These refer to the surfaces at checkout stands that deactivate or remove security tags.
  5. Electro-magnetic fields – Mobile phones, cameras or any items with strong electromagnetic fields also can demagnetize credit card strips.

If the worst happens

If your card happens to become demagnetized, there’s no need to walk away from your purchase. There’s another way to complete the transaction. Try manual entry, the cashier can key the 16 digits on the front of the card into the card reader, along with its expiration date and the CVV number.

However, this is only a short-term solution, if your card happens to become demagnetized the card holder must inform their bank and they will issue another one.

Goudsmit UK

At Goudsmit UK we sub-contract manufacture a vast variety of magnets and magnetic assemblies to suit your requirements. Contact us today for more information at info@goudsmit.co.uk or on +44 (0) 2890 271 001.

For more information download our products and services brochure.

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