DStat: A Versatile, Open-Source Potentiostat for Electroanalysis and Integration
Fig 3
Cell current conversion to voltage for ADC.
(a) Current measurement by shunt resistor. The measurement resistor RM causes a voltage drop proportional to the cell current i by Ohm’s Law. The voltage drop is measured across the resistor but the counter electrode voltage VCE (present on both sides of the resistor) complicates measurement. (b) Current measurement using a transimpedance amplifier. The measurement resistor RM is placed in a negative feedback loop of an op amp (U3) whose inverting input is connected to the working electrode. U3’s non-inverting input is tied to ground, producing a virtual ground at the inverting input. When current i flows through the working electrode, it induces a voltage drop VR across RM, which is balanced by U3 output VO to maintain the virtual ground at its inverting input.