This master's thesis presents the development and testing of a measurement system for time-resolved monitoring of electric current during anodic oxidation experiments. The current is determined indirectly from the voltage drop across external four-terminal shunt resistors. The system is based on a Keysight DAQ970A data acquisition unit with a DAQM909A module, while data acquisition and processing are automated using software developed in Python.
Several four-terminal shunt resistors were characterized, and the effects of the connection method, voltage offset, and polarity reversal were investigated. Two 10-Ω shunt resistors were used for the final measurements, with characterized working resistance values of 10,1177 Ω for channel 301 and 10,1193 Ω for channel 302.
The measurement chain was evaluated using zero-signal measurements, both polarities, and time-based block acquisition. At low signal levels, the voltage offset of the complete measurement path was found to be an important influence. The practical measurement accuracy at currents of a few milliamperes was estimated to be approximately 0,5 %.
The system was applied to anodic oxidation experiments using channels 301 and 302. The measured currents were mostly in the range of approximately (2,4–2,8) mA. The system enabled detection of initial transient behaviour, monitoring of the current over time, and calculation of transferred electric charge. The results indicate that a 10-Ω shunt resistor is a suitable practical choice for the observed current range.
The developed system provides a basis for further multi-channel current monitoring in anodic oxidation experiments, with possible future improvements including higher time resolution and the use of all four channels of the DAQM909A module.
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