DEMAGNETISERS / MD SERIES PRODUCT DESCRIPTION

Overview

Demagnetisers are used with a demagnetising fixture or coil to demagnetise both ferrous and permanent magnet material as individual magnets or as part of an assembly.

Hirst Magnetic Instruments Ltd.  range of MD demagnetisers are capacitive discharge based demagnetisers that utilise a decaying sinusoidal waveform to achieve demagnetisation.

Each demagnetiser in the series is fully microprocessor controlled with adjustable voltage from 50v to maximum in 1v steps, with digital voltage display and adjustment controls.  The microprocessor manages the charging and discharging of the machine ensuring that the charging is managed in a way to reduce the initial charge current that non-microprocessor systems may have.  The microprocessor also performs fault monitoring for system protection.
Each demagnetiser is fitted with an internal dump resistor to discharge the main capacitors in power down or abort mode, ensuring a safe environment for both operator and machine.

The conventional method of demagnetising Alnico and Ferrite magnets is to use a capacitive discharge demagnetiser using a single demagnetising pulse.  Rare earth magnets such as Neodymium Iron Boron or Samarium Cobalt need capacitive discharge demagnetisers capable of delivering multiple pulses.

The MD series (as defined by the energy output, in joules, to the demagnetising fixture i.e. MD4kJ), which is based on electrolytic capacitor technology, is capable of low and medium production rates.  The typical range of energy outputs for the above series span from 750J to 20kJ.

Principles of operation

A Capacitor bank is charged up to a desired voltage.  This stored energy is then released into the demagnetisation fixture via a thyristor.  The energy passes through the fixture, generating a magnetic field, then into the other side of the capacitor bank.  A diode in parallel with the thyristor allows the reverse energy to flow back through the fixture. The energy level reduces with resistive losses in the fixture producing a decaying sinusoidal waveform.

For rare earth demagnetisation the process is repeated with lower energies for each subsequent pulse.

User Interface

The MD demagnetiser series features an easy to use user interface that includes:

• Four Buttons Operation Control
  • Pulse (Green) – to initiate a magnetisation cycle
  • Abort (Red) – to abort the current sequence
  • Up and Down (Yellow) – allows the adjustment of system voltage.
• LCD display – shows the current voltage level, status and error messages
• Key switch – available as an option to lock the adjustment buttons