Magnetic Field Cancellation Systems for SEM, TEM and MRI

Shielding from low frequency (electro) magnetic fields for highly sensitive devices and applications

Bilz offers magnetic field measurement as well as effective and reliable AC+DC magnetic field cancelling systems for highly sensitive devices and applications such as electron microscopes (SEM, TEM, FIB), magnetic resonance imaging (MRI), nanotechnology and biomagnetic examinations.

Environmental disturbances are measured with a sensor positioned near the instrument to be protected and are cancelled by a real-time reverse field generated with a feedback controller and cable loops (or room coils) positioned around. The cancellation is continuous and can adapt to fluctuating disturbances.

This method is an effective and cost-efficient alternative to expensive magnetic field shielding, for example with mu-metal.

 

How do magnetic fields arise?

Besides natural magnetic fields that exist everywhere in the universe, the majority of problems encountered when operating sensitive devices arise from low-frequency magnetic fields that are caused by human activities, such as those emanating from electrical power cables, railways vehicles, elevators, etc. These fields occur as soon as electricity flows through a conductor.
Without suitable shielding, they expand outwards in a circular form and are quite capable of passing through most materials unhindered.

 

Active magnetic field cancellation: cost-efficient and effective

Magnetic field compensation has established itself as the most cost-effective solution. With this method the magnetic field is continuously measured and a compensation device, which includes the necessary control electronics and power amplifier for the direct connection of compensation coils, generates an opposing field. The compensation coils can be made of coiled cables that are laid at the edges of the laboratory, or as a complete solution integrated in a self-supporting aluminium frame.

ohne Magnetfeldkompensation

Imaging problems without magnetic field compensation (SEM picture)

mit Magnetfeldkompensation

Better quality with magnetic field compensation (SEM picture)

Spulenrahmen Magnetfeldkompensation

Applications

  • Image enhancement in electron microscopy (SEM and TEM)
  • Electromagnetic interference (EMI)
  • Biomagnetic applications
  • Compensation of mains frequencies (50/60 Hz) and harmonic waves
  • Suppression of slow and stepped magnetic fields caused by vehicles, moving magnetic objects, elevators, etc.
  • A special version for MRI applications is available
Magnetfeld Kompensationssystem

Bilz magnetic field compensation system

  • 3 axis automatic real-time compensation of low frequency magnetic field disturbance
  • Frequency range from DC to 1 kHz (10 kHz for our FAST version)
  • Fluxgate magnetic field sensor with sub Nano Tesla resolution
  • Controller mode: AC, DC, AC+DC
  • >60 dB near DC
  • >40 dB at 50 Hz (>55dB for our FAST version)
  • Robust analog design, without crash
  • Compensation coil connection capability
  • Measured value and alarm display

For further information about our products and installation services please contact us to arrange a personal consultation.

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