There is described an
electronic interface device (1) for reading an output
signal and controlling and conditioning a three-
electrode amperometric sensor (S). The device (1) may be used with a sensor having an electro-chemical
cell comprising a
reference electrode (RE) configured to supply a constant
cell electric potential to the
electrochemical cell; a
working electrode (WE) at which oxidation or reduction reactions occur, connectable to a first reference
voltage; and a collector
electrode (CE) configured to deliver or receive
electric charge carriers. In the electro-chemical
cell, a
cell impedance (Zcw) is always present between the
working electrode (WE) and the collector
electrode (CE).The device (1) comprises an
operational amplifier (U), having a non-inverting input (u1), adapted to receive a biasing
electric potential (VBIAS) depending on the type of electrochemical reaction of the sensor, and an inverting input (u2) connectable to the
reference electrode (RE) of the sensor. The
operational amplifier is adapted to operate in a feedback configuration to supply the
reference electrode (RE) with the aforementioned constant cell
electric potential on the basis of the biasing electric potential (VBIAS).The device (1) further comprises a first MOS
transistor (M1), having a first MOS gate terminal (G1) connected to the output of the
operational amplifier (U), a first MOS drain terminal (D1), connectable to a second reference
voltage, and a first MOS source terminal (S1), connectable to the collector electrode CE of the sensor (S) to receive or supply a first MOS
transistor channel current (I1) representative of (for example equal to) the cell current (I) which is generated in the amperometric sensor (S).The device (1) further comprises a second MOS
transistor (M2) having a second MOS gate terminal (G2) connected to the output of the operational
amplifier (U) and to the aforementioned first MOS gate terminal (G1), a second MOS source terminal (S2), connectable to the first reference
voltage by means of a first
resistor (R1), and a second MOS drain terminal (D2), connectable to the second reference voltage (for example, through a
resistor R2 which allows the reading of a voltage proportional to the current).The value of the first
resistor (R1) is lower than the
cell impedance (Zcw) so that the second MOS
transistor channel current (I2) depends on the first MOS
transistor channel current (I1), representative of the cell current (I) of the sensor, through a
nonlinear gain dependent at least on the value of the first resistor (R1).The second MOS transistor (M2) is of the same type as the first MOS transistor (M1).Also described is a method for reading an output and
control signal of a three-electrode amperometric sensor, carried out by the aforementioned device.