Inventors:
Wallace H. Coulter - Miami Springs FL
Carlos M. Rodriguez - Miami FL
Assignee:
Coulter Electronics Inc. - Hialeah FL
International Classification:
G01N 2700
Abstract:
A circuit, which is useful to provide data needed to measure the electrical opacity of a particle, for instance a blood cell, passing through a Coulter type transducer, includes a current source for providing a conventional d. c. current through the sensing aperture of the transducer, as well as an oscillator for providing a high frequency current through the aperture. The oscillator includes an active device and a resonant circuit, and the aperture is coupled in parallel with the resonant circuit of the oscillator. The oscillator can be any type of oscillator, such as a Hartley oscillator. As a particle passes through the aperture, the resistance of the aperture increases, which in turn, increases the Q of the oscillator circuit, whereby the oscillator output signal is amplitude modulated in accordance with the increased Q. This amplitude modulated signal can be detected to provide a value based on the high frequency reactance of the particle being detected. The change in d. c.