Abstract: A method is described for enabling leak detection of an underground storage tank surrounded by a water table. The method begins by sealing a test probe in the tank, the test probe having an elongated substantially hollow core with first and second ends, a housing for receiving the second end of the hollow tube and being vented to the fluid product, a low temperature coefficient medium supported in the substantially hollow core of the elongated tube, and a liquid seal supported in the housing between the medium and the fluid product. The method continues by then establishing and maintaining a pressure equilibrium between the hollow core of the test probe and the head space. An inert gas such as nitrogen is then introduced into the head space to overpressurize the head space by an amount sufficient to reestablish a leak at any break in the storage tank despite presence of the water table surrounding the storage tank. Once the tank contents are stabilized, the precision leak test is performed.

Abstract: A test probe is described for substantially eliminating measuring inaccuracies in a storage tank leak detection system caused by temperature-induced volumetric changes in the stored fluid product. The apparatus comprises an elongated tube, formed of a low temperature coefficient material, supported in the storage tank and having first and second ends and a substantially hollow core. A housing is attached to the second end of the elongated tube and is vented to the fluid product such that a portion of the fluid product enters the housing. An inner tube is located within the elongated tube and has an opening connected to the housing. The inner tube is preferably supported within an outer tube and the inner and outer tubes are separated by an evacuated space to provide thermal isolation of the inner tube from the elongated tube. A low temperature coefficient medium is then supported in the inner tube.

Abstract: An apparatus for automatically dispensing flowable material from a disposable container includes a novel electronic control circuit for providing improved and more efficient operation over prior art devices. The electronic control circuit includes a photoelectric emitter, and a phototransistor detector adapted to receive energy reflected from a target such as a user's hands. The control circuit includes a first timing circuit for periodically activating the detector for a predetermined first time period equal to approximately one percent (1%) of the period between operating cycles of the detector. The control circuit also includes a second timing circuit, triggered by the first timing circuit, for activating the emitter during a latter portion of the first time period during which the detector is activated to thereby enable the detector to stabilize after power up.

Abstract: An improved apparatus for substantially eliminating measuring inaccuracies in a storage tank leak detection system caused by temperature-induced volumetric changes in the stored fluid product is described. The apparatus comprises an alongated tube supported in the storage tank and having first and second ends and a substantially hollow core. The apparatus also includes a housing supported in the storage tank for receiving the second end of the elongated tube. The housing is vented to the fluid product such that a portion of the fluid product enters the housing. According to the invention, a medium is supported in the substantially hollow core of the elongated tube, the medium having a temperature coefficient substantially lower than the temperature coefficient of the fluid product.

Abstract: An improved method and apparatus for precision ranging is described using a frequency-modulated signal source to stimulate creation of interference fringes at a rate proportional to absolute distance to a target. According to the invention, a low frequency modulating signal modulates a relatively high frequency signal source having a predetermined long coherent length compared to the distance to be measured. The resulting frequency-modulated signal is transmitted to the target to generate a reflected version thereof. Because of the long coherent length of the signal source, the transmitted frequency-modulated signal maintains spatial coherence as it travels to and from the target. Moreover, the low frequency modulating signal stimulates production of 360.degree. instantaneous phase differences between the transmitted and received frequency-modulated signals when these signals are superimposed. The number of these 360.degree.

Abstract: An interface circuit for use in connecting a high frequency piezoelectric transducer to an input stage of an echo ranging system is described. The circuit includes first, second and third control transistors which are selectively switched by a state controller to control the operation of the circuit. The first transistor is controlled to generate a coherent acoustical pulse at a first predetermined time. The second transistor is controlled to damp the transducer output at a second predetermined time following the first predetermined time. The third transistor serves to clamp the input stage of the echo ranging system to ground until the pulse signal has been effectively transmitted. This operation insures the transducer is in a condition to immediately receive an echo pulse despite the proximity of the transducer to the target whose range is being measured.

Abstract: An improved flowmeter for measuring the flow rate of a fluid in a fluid path is described. In the preferred embodiment, the flowmeter includes a housing having a longitudinal bore therein. A turbine assembly is supported for rotation in the longitudinal bore and includes one or more conductive blades. An inductor coil is supported adjacent the longitudinal bore, and an oscillator is coupled to the inductor coil for generating a signal of predetermined RF frequency in the inductor coil to induce a magnetic field in the bore. In operation, when the fluid is directed through the longitudinal bore, the blades of the turbine assembly are rotated at a speed proportional to flow rate to generate a sensed signal in the inductor coil. The sensed signal includes a low frequency amplitude-modulated signal component proportional to the flow rate of the fluid.

Abstract: A method and apparatus for substantially eliminating measuring inaccuracies in a storage tank leak detection system caused by temperature-induced volumetric changes in the stored fluid product is described. In a preferred embodiment of the method, a limp bladder is connected to an end of a pressure tube having an inlet and a substantially hollow core. The pressure tube and the bladder are filled with a medium having a temperature coefficient substantially lower than the temperature coefficient of the fluid product. The pressure tube and the bladder are then supported in a substantially vertical manner in the storage tank such that a first portion of the medium is supported in the bladder in static equilibrium with respect to a second portion of the medium supported in the pressure tube. The large disparity between the temperature coefficients of the medium and the fluid product insures that temperature-induced volumetric changes in the fluid product do not vary the level of the medium in the pressure tube.