DC/RF blood cell detector using isolated bridge circuit having automatic amplitude and phase balance components

For use with a system in which a carrier fluid containing particles is supplied to a flowcell having a measurement aperture, a circuit for detecting an attribute of a particle present in said measurement aperture of said flowcell comprising:

• a bridge circuit having circuit branches thereof coupled to a source of electrical energy including radio frequency (RF) energy, said bridge circuit having said flowcell coupled therein, and including an electrical balancing circuit that is configured to electrically model said flowcell, and controllably balance variations in amplitude and phase in electrical behavior of said flowcell for changes therein, said electrical balancing network including a controllably adjustable amplitude balancing circuit and a controllably adjustable phase balancing circuit coupled therewith;
• and
• a detector circuit coupled to said bridge circuit and being operative to generate an output signal representative of said attribute of a particle present in said flowcell in accordance with a change in impedance of said flowcell associated with the presence of said particle in said measurement aperture, and including a signal discriminator circuit that is operative to extract respective amplitude and phase components of a signal representative of said change in impedance of said flowcell, and to controllably adjust said amplitude balancing circuit in accordance with said amplitude component, and to controllably adjust said phase balancing circuit in accordance with said phase component, so as to automatically compensate for amplitude and phase variations in said electrical behavior of said flowcell.

For use with a system in which a carrier fluid containing particles is supplied to a flowcell having a measurement aperture, a method for detecting an attribute of a particle present in said measurement aperture of said flowcell comprising the steps of:

• (a) providing a bridge circuit having branches thereof coupled to a source of electrical energy including radio frequency (RF) energy;
• (b) installing said flowcell in a branch of said bridge circuit;
• (c) installing in a branch of said bridge circuit an electrical balancing circuit, that is configured to electrically model behavior of said flowcell for changes in environmental conditions of said flowcell, and controllably balance variations in amplitude and phase in electrical behavior of said flowcell for changes therein, said electrical balancing network including a controllably adjustable amplitude balancing circuit and a controllably adjustable phase balancing circuit coupled therewith;
• (d) monitoring electrical variations in said bridge circuit and generating an output signal representative of said attribute of a particle present in said flowcell in accordance with a change in impedance of said flowcell associated with the presence of said particle in said measurement aperture;
• and
• (e) extracting respective amplitude and phase components of said output signal representative of said change in impedance of said flowcell, and controllably adjusting said amplitude balancing circuit in accordance with said amplitude component, and controllably adjusting said phase balancing circuit in accordance with said phase component, so as to automatically compensate for amplitude and phase variations in said electrical behavior of said flowcell.