Computer Monitor Display Disturbance

Computer monitors can suffer from magnetic field interference and display a flicker or wobbling effect to the screen image.  This is because most computer monitors use the same technology as your television set, the Cathode Ray Tube (CRT).  The CRT creates the image by steering a beam of electrons towards the screen.  While the electrons are travelling towards the screen they can be deflected by any magnetic field.  This has not caused many problems in the past but the introduction of 'multi-scan' and higher frequency monitors has led to problems where the screen image flickers or sways.

It has taken the computer industry a long time to recognise magnetic fields are a possible cause of this effect and many monitors and computers have been replaced unnecessarily.  Now the pendulum has swung the other way and computer experts are now too quick to blame all their problems upon nearby electrical plant and equipment. 

When this type of interference occurs, the dominant magnetic field source has to be identified.  Once the dominant source has been located then solutions can be formulated.

Where possible, the easiest solution is to increase the distance between the monitor and the source of magnetic interference.  If that cannot be achieved, then attention is focussed on reducing the magnetic field from that source.  Again, if the source cannot be altered, then we have two other solutions to consider.  They are: 

  • To replace the monitor with one we know has a higher level of immunity
  • To add shielding to the existing monitor. 

We can supply monitor shields that provide an effective level of immunity for most situations.  Excellent levels of immunity to interference can be achieved by reducing the strength of the magnetic source and by shielding the monitors.

However, applying shielding to the monitor can leave an underlying problem.  That is, staff can become concerned for their health and safety.  They may start by asking.  "If it can do that to my monitor, what can it do to me?" 

We have the knowledge and experience to address both the monitor magnetic interference problems and the operator's associated health concerns.


© 2005 Electromagnetic Surveys Limited