Ultrasonic liquid level monitoring system

A process for measuring the leak rate of liquid in a container by performing a plurality of qualifying liquid level measurements over a known interval of time, the liquid level measurements being convertible into liquid quantity values, the process for measuring a leak rate comprising:

• positioning an ultrasonic probe into a tank containing liquid, the ultrasonic probe having a length in excess of the depth of liquid to be measured;
• the ultrasonic probe having a transducer coupled to the probe body at a first distance above the bottom end of the probe body;
• driving the transducer with a substantially sinusoidal voltage pulse, the voltage pulse starting with the same polarity change sequence on each successive liquid level measurement;
• sampling the substantially sinusoidal voltage pulse and providing a start signal corresponding to the sampled voltage pulse crossing a predetermined threshold;
• receiving an echo returning from the surface of the liquid to the transducer, the transducer providing a corresponding substantially sinusoidal echo signal, and conditioning the echo signal to provide an amplified signal;
• providing a stop signal corresponding to the amplified signal first crossing a predetermined reference level in a predetermined direction and then crossing a second predetermined reference level with a predetermined change in polarity;
• and
• means for measuring the time between the start and stop pulses.

An ultrasonic probe for insertion into a tank for the measurement of the depth of liquid stored in the tank, the probe comprising:

• a probe body in the form of a closed tube with a central longitudinal axis, a top end and a bottom end, and a length in excess of the depth of the liquid to be measured;
• means for holding the probe body in a fixed reference position within the tank, the probe body extending downward vertically through the surface of the liquid, the bottom end of the probe body being held in contact with the base of the tank;
• and
• transducer means coupled to the probe body at a first distance above the bottom end of the probe body for transmitting bi-directional pulses along the longitudinal axis to the surface of the liquid and to the bottom end of the probe body, and for receiving echoes from the bottom end of the probe body and from the surface, the transducer means comprising:
• an ultrasonic transducer having a top surface and a bottom surface;
• and
• a damping washer, having a hole;
• the damping washer being positioned onto the bottom surface of the ultrasonic transducer, the bottom surface of the ultrasonic transducer being directed toward the bottom of the probe body through the damping washer hole, and the hole diameter being selected to provide a predetermined level of attenuation of transmitted signal energy in the downward direction;
• and
• encapsulation means for sealing the ultrasonic transducer and damping washer into a fixed parallel plane relation, the ultrasonic transducer and the damping washer being protected from liquid in the tank.

An ultrasonic probe for insertion into a tank for the measurement of the depth of liquid stored in the tank, and for the detection of leaks in the tank in excess of a predetermined limit, the probe comprising:

• a tubular probe body with a central bore along its longitudinal axis, the probe body having a top end and a bottom end, and a length in excess of the depth of liquid to be measured, the probe body having a back ranging target at the bottom end;
• means for holding the probe body in a substantially vertical position within the tank, the probe body extending downward vertically through the surface of the liquid, the bottom end of the probe being held in contact with the base of the tank;
• transducer means, coupled to the probe body at a first distance above the bottom end, for transmitting bi-directional pulses along the longitudinal axis to the surface of the liquid and to the bottom end, the back ranging target being positioned to reflect a portion of the bi-directional pulses back to the transducer means, and the transducer means being operable to receive echoes from the back ranging target and from the surface of the liquid;
• and
• a cable guideway mounted longitudinally on the outer surface of the probe body from the top end to a point above the transducer means, the cable guideway having a hollow cross section for passing a cable from the top end of the probe body to the end of the cable guideway above the transducer means, the cable passing to the transducer for connection to the transducer means.

An ultrasonic probe for insertion into a tank for the measurement of the depth of liquid stored in the tank, and for the detection of leaks in the tank in excess of a predetermined limit, the probe comprising:

• a probe body of tubular cross section with a central bore along its longitudinal axis, the probe body having a top end and a bottom end, and a length in excess of the depth of liquid to be measured, the probe body having a back ranging target at the bottom end;
• means for holding the probe body in a substantially vertical position within the tank, the probe body extending downward vertically through the surface of the liquid, the bottom end of the probe being held in contact with the base of the tank;
• transducer means, coupled to the probe body at a first distance above the bottom end, for transmitting bi-directional pulses along the longitudinal axis to the surface of the liquid and to the bottom end, the back ranging target being positioned to reflect a portion of the bi-directional pulses back to the transducer means, the transducer means being operable to receive echoes from the back ranging target and from the surface of the liquid;
• and
• a temperature measuring circuit operable to provide a signal indicative of a temperature value.

An ultrasonic probe for the measurement of the depth of liquid stored in an underground tank having a standpipe and for the detection of leaks in the tank in excess of a predetermined limit, the standpipe having an interior wall with an inwardly extending member, the probe comprising:

• a probe body of tubular cross section sized for passage through the standpipe, the body having a central bore along its longitudinal axis, a top end, and a bottom end, and a length in excess of the depth of liquid to be measured, the probe body having a back ranging target at the bottom end of the body;
• holding means for holding the probe body in a substantially vertical position within the tank, the probe body extending downward vertically through the surface of the liquid, the bottom end of the probe being held in contact with the base of the tank;
• and
• transducer means coupled to the probe body at a first distance above the bottom end, for transmitting bi-directional pulses along the longitudinal axis to the surface of the liquid and to the bottom end of the probe, the back ranging target being positioned to reflect a portion of the bi-directional pulses back to the transducer, and the transducer being operable to receive echoes from the back ranging target and from the surface of the liquid;
• wherein the holding means comprises:
• a guide bushing having an inner bore and an outer diameter sized for installation into the probe body bore near the top end of the probe body;
• a compression rod having top end and a bottom end, the compression rod being slideably engaged in the guide bushing bore, with the bottom end of the compression rod being disposed in the probe body bore above the liquid level;
• a clamp disk coupled to the top end of the compression rod, the clamp disk having a diameter selected for insertion into the interior of the standpipe, the clamp disk having at least one notch for complementary receipt and rotary engagement under the inwardly extending member on the standpipe interior wall;
• an adjusting collar positioned and locked onto the compression rod at a position between the compression rod top end and the top of the guide bushing;
• and
• a coil spring positioned coaxially on the compression rod between the top of the guide bushing and the bottom of the adjusting collar, the spring length and spring constant being selected to place the spring in compression when the probe body is passed into the standpipe with its bottom end resting on the bottom of the tank and with the clamp disk in the standpipe bore engaged against the inwardly-extending member.

An ultrasonic probe for insertion into a tank for the measurement of the depth of liquid stored in the tank, the probe comprising:

• probe body in the form of a closed tube of substantially uniform cross-section, having an elongated shape with a central longitudinal axis, the probe body having a top end and a bottom end at opposing ends of the body, and a length in excess of the depth of the liquid to be measured;
• means for holding the probe body in a fixed reference position within the tank, the probe body extending downward vertically through the surface of the liquid, the bottom end of the probe body being held in contact with the base of the tank;
• transducer means coupled to the probe body at a first distance above the bottom of the probe body for transmitting bi-directional pulses along the longitudinal axis to the surface of the liquid and to the bottom end of the probe body, and for receiving echoes from the bottom end of the probe body and from the surface;
• and
• at least a first calibration reflector within the probe body at a second predetermined distance along the longitudinal axis from the transducer.

An ultrasonic probe for insertion into a tank for the measurement of the depth of a petrochemical liquid stored in the tank, and for the detection of leaks in the tank in excess of a predetermined limit, the probe comprising:

• a probe body of substantially tubular cross-section with a central bore along a longitudinal axis extending between a top end and a bottom end, the length of the probe being greater than the depth of the liquid to be measured;
• a back-ranging target at the bottom end of the probe body;
• means for holding the probe body in a substantially vertical position within the tank, the probe body thereby extending downwardly through the surface of the liquid, with the bottom end of the probe body being held in contact with the base of the tank;
• transducer means coupled to the probe body at a first distance above the bottom end, for transmitting bi-directional pulses along the longitudinal axis to the surface of the liquid and to the bottom end of the probe body, the back-ranging target being positioned to reflect a portion of the pulses back to the transducer means, the transducer means thereby receiving echoes from the back-ranging target and from the surface of the liquid;
• and
• a calibration rod passing through the probe body transverse to the longitudinal axis, and positioned at a predetermined distance between the top end of the probe body and the transducer means.