A circuit that offers visual indication of fluid level in a vessel, with a switchable audible alarm. Example uses would be to monitor the level of water in a bath or cold storage tank. Conductance is the reciprocal of resistance. The conductance of fluids vary with temperature, volume and separation distance of the measurement probes. Tap water has a conductance of about 50 uS / cm measured at 25 ° C. This is 20k/cm at 25 ° C. See this site for more details about the conductance of fluids.
This circuit will trigger with any fluid with a resistance under 900K between the maximum separation distance of the probes. Let me explain further. The circuit uses a 4050B CMOS hex buffer working on a 5 volt supply. All gates are biased off by the 10M r