Patent ID: 7459918

Claim:
An impedance measurement system for measuring the complex impedance of each well of a microtiter plate, the microtiter plate wells being formed in an array of rows and columns, the microtiter plate having a topside and an underside, the microtiter plate comprising sensors in the well bottoms and contact pads on the underside of the microtiter plate, the impedance measurement system comprising: (1) at least one daughter board comprising measurement and multiplexing circuitry, each daughter board being associated with a particular row of wells on the microtiter plate, the at least one daughter board lying in a plane perpendicular to the plane of the microtiter plate; (2) at least one top contact board, each top contact board assembly providing an interconnection means between a sensor associated with a particular well in a particular row and the daughter board associated with the row, the at least one top contact board lying in a plane which is parallel to the plane of the microtiter plate, above the at least one daughter board, and below the microtiter plate; (3) a motherboard comprising signal generation and signal processing circuitry, the mother board lying in a plane which is parallel to the plane of the microtiter plate and below the at least one daughter board; (4) a cell plate contact array providing a means for electrical connection between the at least one printed circuit board assembly and the microtiter plate contact pads; (5) a means for thermal control; and (6) a means for system impedance drift compensation comprising at least three resistor-capacitor networks.