Abstract: A system for detecting the fluid level in an intravenous bottle wherein a disposable electrode assembly, consisting of a piece of tape having upper, middle and lower electrode strips, is adhered to the bottle and connected to sensing equipment. The upper strip is longer than the middle strip and the middle strip is longer than the lower strip, so that the capacity between the upper and middle strips (C.sub.1) is normally greater than that between the middle and lower strips (C.sub.2). The sensing equipment includes a bias capacity (C.sub.3) connected between the middle and lower strips so that C.sub.1 is less than C.sub.2 plus C.sub.3 except when the tape is on a bottle with the fluid level in the bottle above the top strip. Pulses having a gradually sloped leading edge and a steep trailing edge are fed to the centre strip.