A self-calibration water level measurement using an interdigital capacitive sensor

• We propose an interdigital capacitive sensor for water level measurement.
• This sensor has low-cost, low-energy, good repeatability, and high linearity.
• This sensor can directly be applied to various types of water without recalibration.
• This sensor can measure water level with 0.2 cm resolution.
• This sensor is also sensitive enough to trace the variability of water level.

A water level measurement using an interdigital capacitive sensor with low-cost, low-energy, good repeatability, high linearity, and ease of installation is proposed with a support of experimental results. This sensor comprises a printed circuit board (PCB) with configuration of two interpenetrating comb electrodes. The comb electrode is 70–80 mm width, 300 mm height with 1–2 mm spacing between each comb. This configuration of electrode causes the capacitance between comb electrodes to vary by the water level. Microcontroller is used to calculate the capacitance between comb electrodes in terms of a discharge time correlated to the water level. A practical water level measurement technique using two comb electrodes designated as level and reference sensors is presented. This technique can directly be applied to water with different conditions without recalibration. This sensor is able to measure absolute levels of water with 0.2 cm resolution over 30 cm range. In addition, it is also sensitive enough to trace the variability of water level. A flood monitoring simulation is carried out in wave flume where this sensor is used to detect the rising wave.