Patent ID: 8423105

Claim:
A sensor comprising at least one sensor unit, each sensor unit comprising: a charge storage element; a first circuitry part connected between said charge storage element and a first measurement element recording a measurement signal, said first circuitry part being provided for periodically applying a first measurement current indicative of a first recorded measurement value to said charge storage element for charging said charge storage element, said first circuitry part comprising a first switching element; a second circuitry part connected between said charge storage element and either said first measurement element or a second measurement element recording said measurement signal, said second circuitry part provided for periodically applying a second measurement current indicative of a second recorded measurement value to the charge storage element for discharging said charge storage element, said second measurement current consisting of components to be eliminated from said first measurement current, said second circuitry part comprising a second switching element; said first and second switching elements being switchable between a conducting state and a non-conducting state; a third circuitry part connected between said charge storage element and an output of said sensor, said third circuitry part comprising a third switching element switchable between a conducting and a non-conducting state; and control circuitry for applying voltages to said first and second switching elements according to a predetermined periodic timing scheme, such that in each period of said timing scheme said first and second switching elements are switched to the conducting state for a given time and that the charge stored on said charge storage element as a result of the components to be eliminated from the first measurement current is substantially equal to said charge which is removed from the charge storage element as a result of the second measurement current; wherein: said charge storage element and said first, second and third circuitry parts are made of organic materials, each of said switching elements in each sensor unit having an uncertain threshold voltage, said conducting and non-conducting states being located on opposite sides of a predetermined voltage range containing said uncertain threshold voltage; said control circuitry is adapted for applying voltages to said switching elements outside said predetermined voltage range; and said third switching element is arranged for conducting charge stored on the charge storage element to said output, said third circuitry part being designed for periodically conducting said charge after a predefined number of said periods.