Method and apparatus for ultrasonic material level measurement

In the method of monitoring the level of material in a storage tank on the basis of the roundtrip transit time of an ultrasonic pulse between a transudcer and the upper surface of said material, the improvement comprising the steps of:

• transmitting a sequence of ultrasonic pulses toward an upper surface of said material,
• receiving echo response pulses reflected from said surface,
• converting each of said echo response pulses to a digital number having a value indicative of the intensity of each of said pulses relative to one another,
• integrating said response pulses from successively transmitted pulses of said sequence according to apparent distance to said surface,
• selecting an integrated response pulse having highest digital value after termination of said pulse sequence, and
• identifying the apparent material surface distance which is associated with said highest-value integrated pulse and treating said apparent distance as actual material surface distance.

In a method of monitoring the level of material in a storage tank as a function of the round-trip transit time of an ultrasonic pulse between a transducer and the upper surface of said material, the improvement comprising the steps of:

• a. transmitting a first ultrasonic pulse having a first pulse width and a first pulse repetition period vertically toward said upper surface of said material,
• b. monitoring for an echo pulse in response to said first transmitted pulse for a preselected time after said transmitted pulse which corresponds to a preselected distance range to said surface,
• c. retransmitting said first ultrasonic pulse in response to an echo pulse within said preselected time,
• d. transmitting a second ultrasonic pulse having a second pulse width different from said first pulse width and a second pulse repetition period different from said first pulse repetition period vertically toward said surface in response to an absence of said echo pulse within said preselected time, and
• e. monitoring for an echo pulse in response to said second transmitted pulse.

A control system for use in monitoring the level of material in a storage tank comprising,

• transducer means mounted at the top of said tank directing ultrasonic pulses downwardly through air toward and receiving echo response pulses reflected upwardly through air from an upper surface of said material,
• means operatively connected to said transducer means to sample said echo response pulses at preselected intervals corresponding to apparent distance from said transducer means to said material surface,
• means converting said sampled response pulses to digital signals each having a numerical value indicative of the intensity of a corresponding response pulse relative to the other sampled response pulses,
• means operatively connected to said transducer means transmitting a first ultrasonic pulse having a first pulse width and a first pulse repetition period downwardly toward said material surface,
• means operatively connected to said converting means comparing digitized echo response pulses from said first transmitted pulse to a preselected response threshold within a preselected time interval after said transmitted pulse, said time interval corresponding to a preselected distance range from said transducer means to said surface,
• means operatively connected to said comparing means and to said first pulse transmitting means retransmitting said first pulse in response to a digitized echo pulse from said first transmitted pulse above said threshold and within said interval,
• means operatively connected to said transducer means and to said comparing means transmitting a second ultrasonic pulse having a second pulse width and a second pulse repetition period in response to an absence of a digitized response pulse from said first transmitted pulse above said threshold and within said interval,
• means operatively connected to said converting means integrating digitized response pulses from said second transmitted pulse over a predetermined pulse sequence of second transmitted pulses according to apparent distance of said transducer means from said surface,
• means operatively connected to said comparing means to provide an indication of actual distance to said surface in response to a digitized echo response pulse from said first transmitted pulse within said interval, and
• means operatively connected to said integrating means to provide an indication of actual distance to said surface upon completion of said pulse sequence.

Apparatus for measuring distance to an object on the basis of round-trip transit time of a transmitted pulse to said object and back comprising, in combination,

• transducer means directing pulses toward and receiving echo response pulses reflected from said object,
• means operatively connected to said transducer to sample said echo response pulses at preselected intervals which are a function of distance from said transducer means to said object,
• means converting said sampled response pulses to digital signals each having a numerical value indicative of the intensity of a corresponding response pulse relative to the other sampled response pulses, and
• echo peak detector means monitoring said digitized pulses to provide an indication of actual distance, said echo peak detector means comprising first digital storage register means for storing digital data, means operatively connected to said digitizing means comparing a digitized pulse in said digitizing means with digital data stored in said first storage register means, means responsive to said comparing means for storing said digitized pulse in said first storage register means when said digitized pulse is greater than said stored data, second storage register means for storing digital data, and means responsive to said comparing means to store an apparent distance associated with said digitized pulse stored in said second storage register means when said digitized pulse is greater than said stored data.

In a system for monitoring the level of a material on the basis of the round-trip transit time of an ultrasonic pulse between a transducer and a surface of said material, the combination comprising,

• means transmitting a sequence of ultrasonic pulses toward a surface of said material,
• means receiving echo response pulses reflected from said surface,
• means converting each of said echo response pulses to a digital number having a value indicative of the intensity of each of said pulses relative to one another,
• means integrating said response pulses from successively transmitted pulses of said sequence according to apparent distance to said surface,
• means selecting an integrated response pulse having highest digital value after termination of said pulse sequence, and
• means identifying which apparent material surface distance is associated with said highest-value integrated pulse and treating said apparent distance as actual material surface distance.

In a system for monitoring the level of a material as a function of the round-trip transit time of an ultrasonic pulse between a transducer and a surface of said material, the combination comprising,

• means transmitting a first ultrasonic pulse having a first pulse width and a first pulse repetition period vertically toward said surface of said material,
• means monitoring for an echo pulse in response to said first transmitted pulse for a preselected time after said transmitted pulse which corresponds to a preselected distance range to said surface,
• means retransmitting said first ultrasonic pulse in response to an echo pulse within said preselected time,
• means transmitting a second ultrasonic pulse having a second pulse width different from said first pulse width and a second pulse repetition period different from said first pulse repetition period vertically toward said surface in response to an absence of said echo pulse within said preselected time, and
• means monitoring for an echo pulse in response to said second transmitted pulse.

In a control system for use in monitoring the level of material in a storage tank, the combination comprising,

• transducer means directing ultrasonic pulses toward and receiving echo response pulses reflected from the upper surface of said material,
• means operatively connected to said transducer means to sample said echo response pulses from each transmitted pulse at preselected intervals which are a function of the distance of said material surface from said transducer means,
• means converting each of said sampled response pulses to digital signals having a numerical value indicative of the intensity of each said echo pulse relative to other echo pulses similarly received, and
• means monitoring said sampled and digitized response pulses to provide an indication of actual distance, which is a function of material level, upon completion of said pulse sequence, said monitoring means comprising first digital storage register means for storing digital data, means operatively connected to said converting means comparing said converted pulses with digital data stored in said first storage register means, means responsive to said comparing means for storing a converted pulse in said first storage register means when said converted pulse is greater than said stored data, second storage register means for storing digital data and means responsive to said comparing means to store an apparent material surface distance associated with said converted pulse stored in said second storage register means when said converted pulse is greater than said stored data.