Abstract: The marine cable insulation oil sensors are primarily applied for detecting extremely low concentrations of insulating oil in seawater. Compared to conventional water-oil sensors, the detection of insulating oil imposes stricter requirements on sensor calibration processes and the preparation of standard solutions. This paper proposes a novel calibration scheme, featuring a non-contact inverted calibration structure designed to reduce contamination risks, thereby enhancing operational convenience and calibration accuracy. Additionally, ultrasonic emulsification technology is employed to prepare standard solutions, which more closely mimic the naturally formed water-oil emulsion state in seawater oil spill accidents. Furthermore, a systematic investigation into calibration-influencing factors reveals that environmental light interference is negligible, whereas controlling the liquid level height is necessary to mitigate signal interference at the gas-liquid interface. Subsequently comparative analysis with industry-standard methods demonstrates that the relative deviation of the calibration results under this scheme ranges from 6% to 10%, exhibiting excellent accuracy within the target concentration range. This method provides high-reliability technical support for marine ecological environment monitoring.

Key words: Insulating oil, Sensor, Ultraviolet fluorescence method, Calibration