Performance Investigation of a Digital Signal Conditioner with 120 dB Range for Amperometric Sensors

The paper reports the design and performance studies of a digital signal conditioning circuit for amperometric sensors. A number of amperometric sensors provide a current-output having large dynamic span. The proposed circuit is designed to measure sensor currents ranging from 10 pA to 10 µA (dynamic range : 10
⁶
). The circuit comprises a multi-stage transimpedance amplifier cascaded with a secondary integrator amplifier. Apart from wide-span, the salient features of the circuit include a) Simplicity of design, b) reduced effects of quantization error, c) good speed of response and d) bipolar measuring ability. The design, simulation and experimental aspects of the designed circuit is reported in the paper. The circuit, designed for a response time of 15 ms and quantization error ≤0.5 %, was observed to have a maximum non-linearity of 0.88 % in the range ± (10 pA, 10 µA).