Nowadays, with the continuous development of science and technology, the coffee machine has entered thousands of households. In order to make the coffee machine more intelligent, the coffee machine will realize low liquid level reminder and quantitative water output, so how to achieve these two functions? To realize the coffee machine low level remind function need to install a non-contact liquid level sensor, non-contact liquid level sensor can accurately detect the coffee machine water tank, sensor through the principle of capacitance, when the sensor position without water, the sensor will output different voltage signal, to the controller, so as to realize the low liquid level remind function, prompt the user to add water.