Batch fabrication and testing of multiparameter integrated sensor for marine environmental measurements

Miniature and multi-parameter integrated water quality sensors are essential for marine environmental protection, resource exploration and fisheries exploitation. This work describes a miniature sensor integrating conductivity, pH and temperature sensing units with liquid-connected Ag/AgCl reference electrode and thin-film Pt electrode array designed and fabricated by MEMS. The excellent linearity, ideal detection range and satisfactory detection accuracy of the sensor are witnessed after a systematic performance investigation. The sensor is linear with a linearity of 0.999 (C), 0.9999 (T) and 0.998 (pH), is competitive with a detection range of 0.1 to 60 mS/cm (C), -5 to 55 °C (T) and 4 to 10 (pH), is precise with an accuracy of 0.02 mS/cm (C), ± 0.01 °C (T) and ± 0.1pH (pH), respectively. In addition, the effect of temperature on pH and conductivity detection should not be ignored. Therefore, the effect of temperature changes on the sensor is investigated and a circuit module is created to collect and analyse the sensor signal. The stability and accuracy of the sensor is improved by providing real-time temperature compensation. Besides, the sensor behaviour described above, the process compatibility of the physical and chemical sensor units, consistency of batch preparation, power consumption, cost and packaging have all been thoroughly considered in this work. Undoubtedly, the highly accurate, miniaturised, sensitive and mass-produced miniature multi-parameter sensor proposed in this paper is a competitive device in a wide range of marine areas for on-line monitoring of conductivity, temperature and pH in-situ online monitoring.