Fluid Level Detector #2: Circuit is built around2-input NAND
Schmitt trigger gates N1 and N2. Gate N1 is configured as an
oscillator operating at around1 kHz frequency.
Sonar like method detects fluid level: 07/19/2001 EDN -
Design Ideas / Figure 1 illustrates a simple, cost-effective
method of measuring the height of fluid in a column by using
ultrasonic waves. Two piezoelectric transducers generate and
listen to the ultrasonic acoustical wave.