The LM1830 is a monolithic bipolar integrated circuit designed for use in fluid detection systems The circuit is ideal for detecting the presence absence or level of water or other polar liquids An AC signal is passed through two probes within the fluid A detector determines the presence or absence of the fluid by comparing the resistance of the fluid between the probes with the resistance internal to the integrated circuit An AC signal is used to overcome plating problems incurred by using a DC source A pin is available for connecting an external resistance in cases where the fluid impedance is of a different magnitude than that of the internal resistor When the probe resistance increases above the preset value the oscillator signal is coupled to the base of the open-collector output transistor In a typical application the output could be used to drive a LED loud speaker or a low current relay