Liquid level detecting circuit and detecting method

The invention relates to a liquid level detecting circuit and a detecting method, wherein the liquid level detecting circuit comprises an equivalent capacitor, an analog signal processing module and a digital signal processor, wherein the equivalent capacitor is positioned between a sample adding needle and the machine frame land, the analog signal processing module is connected with the equivalent capacitor and is used for processing a voltage signal of the equivalent capacitor into a direct current signal, and the digital signal processor is connected with the capacitor through a resistor, is connected with the analog signal processing module, is used for providing charging and discharging excitation signals for the equivalent capacitor and is used for carrying out analog-digital signal conversion on the direct current signal of the analog signal processing module and determining whether the sample adding needle is in contact with the liquid level of the samples or not according to the converted digital signal. The liquid level detecting circuit and the detecting method adopting the embodiment has the advantage that the liquid level detecting accuracy is improved on the basis of realizing the liquid level detecting automation.