Water is commonly used for industry, agriculture and office and domestic consumption. Water shortage is one of the most worrying problems and it is related to poor management and inefficient use of water resources. Therefore, efficient use and monitoring of water are very important. Here, water level sensing is of key importance. Many physical properties of water like relative electrical permittivity, resistivity, thermal conductivity, buoyancy, hydraulic pressure, absorption of radiation, surface reflection of sound or light waves, etc. are used for water level sensing.
Although a variety of structures of capacitive water level sensor and low capacitance probing techniques have been proposed, it is still important to develop a new type which is more convenient, flexible, simple, low-cost and easy to make for widespread application in homes and offices.
Kim Chol Man, a section head at the Faculty of Earth Science and Technology, has proposed a new low-cost capacitance-type water level sensor and low capacitance probing technique. Unlike the conventional low capacitance probing techniques which involve analog circuits such as AC-bridge, negative impedance converter, analog switch, oscillator, multiplexer, phase shifter, etc., his method is based on a direct capacitance-to-time conversion principle by a single microcontroller unit (MCU).
For test and verification, he made a prototype water level controller. The results of the experiments showed that the repeatability and linearity of the sensor are satisfactory within the tolerable limit of 0.5% full scale.
The prototype water level controller is simple and cheap enough for home and office use.
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