Patent ID: 6750660
Filing Date: 2004-06-15
Classification: G01N

Abstract:
An apparatus for evaluating data representing the electrical characteristics of a combustion vessel, the combustion vessel being operable to combust a fuel, comprising:a matrix of nodes arranged on an ohmic material of the combustion vessel; at least one wire connected to a respective node; a switch connected to the at least one wire and to a current source for controlling the delivery of a current to the respective node via the switch and the at least one wire, the switch having an on state and an off state, the off state allowing a leakage current through the switch; means for preparing a data set based on voltage data gathered from the matrix of nodes arranged on an ohmic material of the combustion vessel including calculating the resistivity of the ohmic material by iteratively imposing a known current to the matrix and measuring voltage at the nodes, each the iteration of imposing a known current resulting in a set of measured voltages; and a circuit for reducing leakage currents in the switch that controls delivery of current to a load, the circuit including: a series component positioned between the switch and the load, the series component permitting delivery of current to the load through the switch and across which series component the leakage current develops a voltage, and an active device connected across the series component to force the voltage across the series component to zero volts by means of feedback control, whereby the leakage current is reduced to an input current of the active device.