The development and implementation of our two-electrode systems not only greatly simplify the fabrication process, but also leads to simplified electronic circuitry for driving and reading the electrochemical transducer. Indeed, due to the fixed potential of the CE, it is not necessary to variably adapt any potentials relative to a reference electrode, as is the case in three-electrode systems. This means fewer components are required to create and operate these two-electrode systems. Since open-source three-electrode potentiostats require at least $40 worth of parts, we see enormous potential for two-electrode systems in significantly lowering the costs associated with creating accessible signal readers. To this end, we designed a reader using only one operational amplifier to apply a constant voltage (361.76±0.05 mV) and monitor the current with 0.2 μA resolution and a range up to 211 μA (Figs. 7a, S18 and S19). The current range (with constant 0.1 % resolution) can be tuned by swapping a single resistance and tailored to a specific application. The system is controlled by an inexpensive microcontroller, resulting in a total part cost of less than $3 (Table ). Remarkably, we can harness the computing power of the reader to not only drive the transducer, but to also analyze results in real time and guide the user through the measurement process using a multicolor LED (Fig. , Supplementary Video 1). In a typical experiment, the reader remains idle until it detects the flow front from the carrier buffer (Figs. and) because of a change in resistivity. It then proceeds to detect the peaks and notifies the user when the current has sufficiently decayed, and the cartridge is ready for the next injection. We also incorporated a stop criterion, which currently simply relies on a time limit, but could detect critical system failures in the future. Remarkably, and despite its simplicity, the $3 reader delivers performance comparable with high-precision benchtop potentiostats (Fig. ). Furthermore, the smart reader streamlines the testing process for operators, and offers the flexibility of standalone operation or realtime communication of results to a display, laptop or smartphone via a USB connection (Fig. ).