Magnets and recommended safety distance

Magnets have different influences on devices: some devices are severely damaged, while others are only temporarily altered. Many of the following items have become an integral part of our lives. We use them on a daily basis and it is useful to know which ones are sensitive to magnetic fields, such as permanent magnets, to avoid unintentional loss of data or other functional impairment.

Hearing aids, pacemakers and magnetic fields

Hearing aid components, e.g. loudspeakers, can be damaged due to the magnetic field strength of 200m Tesla. But also the strengths of 20m Tesla can lead to alterations, which negatively affect the use. Please pay attention to a sufficient safety distance here.

Pacemakers respond to magnets and the physician in charge uses this behavior to perform controls and frequency changes during some cycles. Once the magnet is removed, the pacemaker continues to function as usual. However, as there are many different manufacturers and newer and older models, a general evaluation cannot be performed. In any case, it is safer to stay away from strong magnetic fields and, if in doubt, contact the manufacturer of your pacemaker. Again, it is advisable to keep a distance to the magnets.

Magnetic strips on cards and magnetic fields

The magnetic strips are coated with magnetic metal oxide. You can find them on several plastic cards that almost everyone in your wallet carries and uses every day. Since there are several cards and important data to protect, there are also two different qualities that are used. They are divided into high coercivity (high quality) and low coercivity (lower quality).

The high quality variant is used, for example, for credit and debit cards. The data is erased only with a magnetic force of 0.4 Tesla, but even with a third of the force it can already lead to partial damage. Since magnetic cards can no longer be read correctly in this case, only a coercive field strength of 40m Tesla, i.e. 10% of 0.4 Tesla, guarantees absolute security.

The cheapest variant of low coercitivity can be found, for example, in paper tickets, which are used in car parks or as entrance tickets. The magnetic strips are light brown and much more sensitive than the high quality version. Even a coercive magnetic field strength of 30 m Tesla is sufficient to demagnetize the magnetic stripe and permanently damage the data. Strengths below 3m Tesla provide security against damage to stored data.

Mechanical clocks and magnetic fields

Modern mechanical watches are considered anti-magnetic and are manufactured in accordance with the international standard ISO 764, which corresponds to the German standard DIN 8309. This standard defines the resistance of watches to magnets. Magnetic fields can affect some elements of the mechanical watch, such as the helical spring. According to the standard, anti-magnetic watches, even when exposed to a magnetic field of 6m Tesla, can deviate a maximum of 30 seconds per 24 hours. However, some watch manufacturers offer much less sensitive watch models.

For non-magnetic watches, a defined safety distance cannot be specified. On the safe side, you are here if you put your watch without magnetic field around 0.05m Tesla. This corresponds to the earth's natural magnetic field. If you expose an analog quartz watch to a strong magnetic field, it can happen that the watch motor goes faster or slower, or even stops completely. When the magnet is removed and the watch is manually corrected, the quartz watch will generally run the same.

Smartphones or tablets and magnetic fields

Smartphones, tablets, digital cameras and similar consumer goods generally incorporate mechanical parts and loudspeakers that can be disturbed by very strong magnets, while stored media are safe from magnetic fields. Therefore, keep your electronic devices away from strong magnetic fields when in doubt.

USB Memory, Hard Drives and Magnetic Fields

Magnetic fields do not have a negative impact on data stored on USB sticks. By the way, the same applies to CD and DVD data.

Even hard disks can only be deliberately damaged by a magnetic field, because it has to come very close to the hard disk with a very strong magnet. For this, even the hard disk cover would have to be unscrewed; otherwise, it cannot get close enough with the magnet.

Car keys and magnetic fields

The car key and the built-in technology do not suffer any damage when they come into contact with a static magnet.


In short, magnets are harmless to data stored in mobile phones, tablets and digital cameras. They also have no effect on car keys, USB sticks and hard disks unless handled. However, caution should be exercised with pacemakers, hearing aids and watches.

Web desarrollada por 
Volcanic Internet