Patent ID: 7706989

Claim:
A method of determining when a fluid level in a vessel is surging, the method comprising: providing a probe located in a fluid containment vessel and conductively coupled to said fluid, said fluid containment vessel containing a fluid, said fluid having a stable level, and said fluid surging above said stable level; generating a transmitted signal which passes into said fluid; detecting said transmitted signal at said probe during a time segment; repeating said step of detecting to collect a set of detected probe signals, each of which is associated with a different time segment within a period; determining a probe reading representative of said detected probe signals in said set; determining a dynamic indicator for said set of detected probe signals, said dynamic indicator indicating variability of said detected probe signals in said set compared to said representative probe reading; and using said dynamic indicator to determine if said fluid is surging over said probe when said probe is located above said stable level or if said probe is below said stable level.