High accuracy surface perceiving water level gauge with self calibration

In a water level measuring system, the measured precision will often be decreased along with an increase in measured range. Meanwhile, the cumulative error will also increase after the system has worked form some time. In order to correct these deficiencies, based on designs incorporating self calibration and low-power dissipation, a new water level gauge with wide range and absolute error less than 2 mm was explored and invented. The gauge combines an electric DC motor driving the mechanical structure to perceive the water surface and a rotary encoder counting the distance from benchmark to the water surface sensed. A steel hammer hung by a thin steel cable from the encoder coaxial wheel is used to perceive the water surface with its sharp pin to touch the water through gravity. A self calibration framework results in the measurement being calibrated exactly every time when the gauge works, which not only eliminates the long-term cumulative error but also guarantees the high precision with a wide range. The device is designed as a green wild usable gauge in view of its low power dissipation; it could be powered by a small solar panel. The experimental results and analysis are presented to show the gauge's remarkable features of high accuracy, low-power dissipation and wide range.