This is the first post in our tutorial series on electrochemical measurements. We will walk through the parameter choices that determine whether your EIS measurement is meaningful or just noise.
Step 1: Amplitude selection. The applied AC amplitude must be small enough to keep the system in its linear regime, but large enough to give a measurable response. 5–10 mV RMS is a reasonable starting point for aqueous systems.
Step 2: DC bias. Pick a DC bias that places your sensor in the operating point of interest, often the open-circuit potential or a redox formal potential.
Step 3: Frequency range. Cover the range that captures the timescales of your physical processes. For most aqueous biosensors, 100 kHz down to 0.1 Hz is a good default.
Step 4: Quiet time. Allow the system to settle at the DC bias before starting the sweep, especially after switching potentials.
Step 5: Post-processing. Inspect the Bode and Nyquist plots, fit an equivalent circuit, and report goodness of fit alongside extracted parameters.
