An apparatus includes a detecting electrode, a liquid sensing module, and a connecting means. The detecting electrode is attached to an outer surface of an intravenous drip container. The liquid sensing module includes a clock generator generating a clock signal, a waveform generating circuit coupled to the detecting electrode to generate an analog driving signal by using the clock signal, a grounding electrode grounded through the waveform generating circuit, an analog-to-digital converter converting the analog driving signal to a digital voltage signal, and a capacitance determining circuit receiving the digital voltage signal to determine a value of a capacitance of a capacitor formed by the detecting electrode and the grounding electrode. The connecting means connects the detecting electrode to the liquid sensing module.
