Single transducer liquid level detector

A process for determining the nature of the contents of a container without requiring physical access to the interior of the container;

• said process comprising the injection of a repetitive longitudinal ultrasonic pulse of energy into the wall of said container at a reference location known to have a given internal medium therein;
• measuring the amplitude of the return signal reflected from the inner wall of said container for each pulse, and measuring the attenuation of said return signal to produce a reference attenuation;
• and thereafter injecting a longitudinal pulse of energy into the wall of said container at a second location thereon and measuring the attenuation of the amplitude of the return signal reflected from the inner wall of said container at said second location;
• and comparing the attenuation of said return signal at said reference location and at said second location, and producing an output signal in response to said comparison.

A transducer monitor for monitoring the presence or absence of liquid in a container at a particular location thereon;

• said transducer monitor including a transducer for producing a repetitive longitudinal output pulse of ultrasonic energy, a receiving circuit connected to said transducer for producing a return signal responsive to reflected energy received by said transducer;
• amplifier circuit means connected to said receiving circuit for amplifying said return signal;
• a normalizing circuit means connected to said amplifier circuit means and including first reference voltage means to cause said amplifier circuit means to amplify the first pulse in said reflected signal to a given first reference voltage magnitude;
• attenuation measuring circuit means connected to said amplifier circuit means including a second reference circuit means containing a second reference voltage means;
• the voltage level of said second voltage reference means being lower than that of said first reference voltage means by a given value;
• first comparison circuit means producing an output when said return signal amplitude attenuates to the level of said second reference voltage means;
• attenuation time measuring means for measuring the length of time taken for said return signal to attenuate from said first reference level to said second reference level;
• a reference attenuation time circuit for producing an attenuation time reference related to the presence of a given medium in said container at the point of measurement;
• second comparison circuit means connected to said attenuation time measuring means and said reference attenuation time circuit for comparing the measured attenuation time to the reference attenuation time;
• and output circuit means for producing an output in response to the comparison of times in said second comparison signal.