Potentiometric transducers. These transducers measure the potential difference between a working electrode and a second reference electrode under the condition of zero current flow. There is direct logarithmic relationship between the charge generated at the electrode and the activity of the ion of interest. Since the analyte is not consumed in this device, it is non-destructive technique. There are three types of potentiometric devices : (i) ion-selective electrodes (ISEs), are usually pH meter electrodes, (ii) gas-sensing electrodes  and (iii) field effect transistors (FETs) which are usually solid state electrodes.

Many reactions generate or use up H₊, which is detected and measured by the biosensors using ISEs. The gas sensing electrodes detect and measure the amount of gas produced. In the following reaction, the level of urea can be estimated by (i) NH₄₊ ion sensitive electrodes, or by, (ii) NH₃ or CO₂ gas sensitive electrodes. The technology can also be used for an assay of trace amount of DNA.
CO(NH₂)₂ + 2H₂O + H+ → 2NH₄+ + HCO₃+

These ISEs and gas sensing electrodes are commonly used for a variety of purposes including water monitoring. FETs allow manufacture of miniaturized biosensors, which make use of a silicon-based sensor.