Patent ID: 6611611
Filing Date: 2003-08-26
Classification: G01N,H03G

Abstract:
A particle sensor which detects the presence of specific particles and provides an output signal indicative of the amount of the particles being detected, said particle sensor comprising:a detector proving an output voltage which is proportional to the amount of particles carried on a medium such as the air being detected; a gain controller adjusting the output voltage received from the detector to provide an adjusted output voltage, said gain controller including a gain resistor network which gives a variable resistance in order to vary the adjusted output voltage; an offset voltage adjustor providing an adjustable offset voltage indicative of a background voltage which is combined with said adjusted output voltage to provide a sensor output which satisfies a predetermined (regulation) relationship between a particle density and the sensor output, said offset voltage adjustor comprising an offset resistor network which gives a variable resistance in order to adjust the offset voltage, at least one of the gain resistor network and the offset resistor network comprising a plurality of digitally controllable switches and a plurality of resistors so as to give the variable resistance varying by conduction of a suitable combination of the switches, wherein said particle sensor further including: memory means which stores an instruction data designating which one or more of the switches are to be made conductive; and a memory interface which transfers the instruction data from the memory means to at least one of the gain resistor network and the offset resistor network.