Integrated interdigital electrode and thermal resistance micro-sensors for electric vehicle battery coolant conductivity high-precision measurement

Monitoring the conductivity of battery coolant is extremely important as it can significantly improve the safety of electric vehicles. The conductivity of coolant should be maintained in the range of 0-10 μS/cm to ensure the insulation level, requiring high-precision measurement of ultra-low detection range. However, polarization and capacitive effects, temperature effects, as well as poor stability, all pose significant challenges to achieving high-precision conductivity measurements. This work describes a novel integrated conductivity and temperature (CT) micro-sensor for the conductivity high-precision measurement of electric vehicle battery coolant. An interdigital micro-electrode is fabricated for conductivity sensing and a thin-film platinum resistor is employed as temperature sensor cell. The integrated CT sensor demonstrates an acceptable limit of detection with a resolution of 0.1 μS/cm. Besides, high-precision signal acquisition and processing circuit is designed for sensors and a desirable measuring full-scale error is observed. Compared to the current method of using bulky metal electrodes prepared by mechanical process as conductivity sensor, the proposed sensor can be mass produced by Micro-Electro-Mechanical System (MEMS), and favorable consistency, high sensitivity, excellent stability, smaller size are obtained. Consequently, the as-proposed CT micro-sensor has an opportunity to be developed as a competitive device for online conductivity monitoring in battery coolant.