Principles of Operation
The PDM series generates waveforms which, when analysed,
have continuous mathematical derivatives avoiding discontinuous rates
of change in the applied field and potentially impairing the
demagnetising process. This is achieved using the capacitance
technique with electronic control of the field frequency.
The microprocessor controlled PDM unit generates
frequencies of less than 0.01 Hertz and up to 100 Hertz. The
of the resultant magnetic field is controlled by the microprocessor
programme within the limits of the resultant inductance for any
particular application. For certain applications it may prove
inappropriate to apply higher frequency waveforms.
The PDM microprocessor controller enables operators to
programme demagnetising processes as well as maintaining a non-volatile
memory of pre-programmed processes.
Depending upon the size, coercivity, relative
permeability etc, of a particular body, there will be an optimum
demagnetisation process. If the applied frequency is too high,
demagnetisation will not occur. If the applied rate of decay is
fast or too slow, demagnetisation will not be effective. If the applied
frequency is too low then the overall process could prove prohibitively
To optimise the processing time it may be necessary to
have a range of processes for a range of bodies being
PDM range incorporates the flexibility to optimise these parameters.
Hirst Magnetic Instruments Ltd. Precision
standard control units with variable output powers which are configured
specific to particular applications. Please refer to the factory
your specific requirements.