Method and apparatus for making measurements of accumulations of magnetically susceptible particles combined with analytes
An apparatus is provided for quantitatively measuring samples whose amount or other characteristic quality is to be determined. The samples are arranged in a predefined pattern and are excited in a magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to at least one substantially flat sensor such as sensing coils fabricated in a gradiometer configuration.
1. An apparatus for quantitative magnetic measurement of samples, each sample arranged in a predefined pattern and disposed in a sample holder, comprising:
a magnetic field source to apply a magnetic field to the sample, the magnetic field source defining a gap in which a sample holder is movably disposed;
a substantially flat magnetic field sensor to sense an induced magnetic moment from the sample and configured and arranged in a gradiometer configuration to substantially eliminate the contribution of the magnetic field source to the sensing, the magnetic field sensor having a sensing area substantially the same as the extent of each sample, the magnetic field sensor having an output to communicate output signals to provide quantity of the samples in the pattern, the magnetic field sensor disposed substantially within the gap of the magnetic field source.