Patent ID: 8358216

Claim:
A liquid level detecting device, comprising: a control unit to output one or more control signals corresponding to environmental information that corresponds to where a sampling needle is located in the liquid level detecting device; an amplifying unit that comprises a feedback circuit that is to set a gain according to the one or more control signals, wherein the feedback circuit comprises: a switch, which switches among multiple states or among multiple connections based at least in part upon the one or more control signals and is connected to an output terminal and an inverse input terminal in the amplifying unit, a control terminal, which is connected to an output terminal of the control unit, to transmit a feedback signal to the inverse input terminal of the amplifying unit, and a feedback impedance element connected between the output terminal and the inverse input terminal of the amplifying unit and comprising at least one of a digital or analog potentiometer, a variable capacitor, and a variable inductor to control an impedance value according to the one or more control signals; a conversion unit to receive an electrical signal outputted by the sampling needle and output a corresponding electrical signal after conversion, wherein the amplifying unit is to receive the electrical signal and amplify the electrical signal according to the gain to output the corresponding electrical signal, and the control unit is to receive the corresponding electrical signal and determine whether the sampling needle contacts a liquid level based at least in part upon the corresponding electrical signal.