Fluid level detector

A fluid detector for determining a presence of a fluid within a container having a wall with an outer surface and an inner surface, the fluid detector comprising:

• a piezoelectric element that outputs a first ultrasonic signal in response to an input electrical signal;
• a lens with an upper portion and a lower portion;
• a generally cylindrical wall being integral with and extending outwardly from the outer surface of the wall of the container, the generally cylindrical wall defining a housing with a cylindrical central bore having a base surface adjacent the outer surface of the wall of the container;
• and
• wherein the piezoelectric element is coupled to the upper portion of the lens so that, when the lens is disposed within the cylindrical central bore adjacent the base surface such that the lens is intermediate the piezoelectric element and the wall, the lens focuses the first ultrasonic signal toward the wall so that the first ultrasonic signal enters the wall;
• and
• an ultrasonic detector that, when disposed in a predetermined position adjacent the outer surface of the wall, receives a second ultrasonic signal from the wall that results from the first ultrasonic signal and that is affected in a predetermined manner by presence or absence of fluid at the inner surface of the wall, wherein the ultrasonic detector generates an output electrical signal corresponding to the second ultrasonic signal.