Frequency Response
Analytical measurement techniques that evaluate the electrical response of a system to an alternating current over a broad range of frequencies provide detailed information about internal physical and chemical processes. Performance of impedance spectroscopy allows for the separation of resistive, capacitive, inductive, and electrolytic contributions within a single experiment. This method identifies the distinct time constants associated with charge transfer, mass transport, dielectric relaxation, and film growth.
Component Resolution
Equivalent circuit modeling transforms the raw electrical data into physical parameters such as coating resistance or double layer capacitance. Each element in the circuit corresponds to a specific mechanism occurring at an interface or within the bulk material. Software algorithms fit these models to the data to quantify the health and performance of the sensor or battery.
System Transfer
Signal processing ensures that the input perturbation remains small enough to maintain a linear response from the electrochemical system. Large voltage swings can trigger side reactions that invalidate the measurement. Frequency sweeps must be conducted with sufficient dwell time to ensure stable data acquisition at each point.
Calibration Standard
Accuracy in these measurements depends on the elimination of stray capacitance and lead inductance from the test fixture. Reference resistors with known characteristics are used to verify the instrument. Drift in the measurement electronics can distort the high frequency intercept and lead to errors in the calculated solution resistance.
