Abstract: A method and apparatus for damping an ultrasonic transducer suitable for time of flight ranging and level measurement systems. The ultrasonic transducer comprises a damping component which absorbs vibrations in the transducer to reduce the ringing effect. The damping component is subjected to plasma etching to produce a surface which readily bonds to component(s) of the transducer. According to one aspect, the damping component is formed from an inert elastomer, such as silicone rubber, and the transducer component is made of stainless steel.

Abstract: A microwave-based level measurement system having a planar microwave antenna configuration. According to another aspect, the microwave-based level measurement devices are field interchangeable with ultrasonic based level measurement devices.

Abstract: A method of operating a pulse echo ranging system comprising a transducer assembly for providing transmission and reception of high frequency energy pulses at substantially different plural frequencies. The method uses signals received by the transducer assembly to generate an echo profile for signals received at at least a first of the frequencies to enhance the recovery of data beyond that obtained from the first signal alone.

Abstract: A method and system for high-pass filtering to remove DC and/or low frequency components of a receive signal from the transducer of a level measurement system. In one embodiment, the method includes generating a maximum signal profile and a minimum signal profile for the receive signal, generating a midpoint reference signal from the maximum and minimum signal profiles and subtracting the midpoint reference signal from the receive signal to produce a filtered signal.

Abstract: A loss-less diode equivalent circuit which functions to reduce and eliminate the forward bias voltage or drop associated with conventional diodes. The loss-less diode comprises a reverse connected MOSFET device which is configured with a clamping circuit and coupled to an input stage. The drain is coupled to the input stage which receives an input signal. The source of the MOSFET device provides an output port for charging a capacitor in a conduction or on state.

Abstract: A time-base generator with a self-compensating control loop. The time-base generator is suitable for use in level measurement and time-of-flight ranging systems. The time-base generator includes a pulse generator stage, a delay stage, a control loop and a references voltage module. The pulse generator generates a transmit pulse train and a receive or sampling pulse train with a delayed timing relationship. The control loop functions with the delay stage to maintain the desired delay between the first pulse train and the second pulse train. According to another aspect, the time-base generator includes a calibration module. The calibration module generates calibration pulses which are used by the controller in the level measurement system to calibrate operation.

Abstract: A pulse offset calibration method for a pulse-echo level measurement system. The pulse-echo level measurement system includes a transducer for transmitting calibration acoustic pulses and receiving echo pulses. A receiver converts the echo pulses into corresponding pulse profile signals having a leading edge. A static delay interval is defined on the leading edge corresponding to the time interval between the reception of the echo pulse and the response by the receiver. A dynamic delay interval is defined on the leading edge corresponding to the time response characteristics of the transducer and the receiver. The static delay interval and the dynamic delay interval are summed to determine the offset time interval for the echo pulse. The offset time interval is subtracted from the measurements to provide the true duration for the time of flight.

Abstract: A method and system for echo processing a receive signal using autocorrelation. A receive signal is sampled, digitized and high-pass filtered. A correlation signal is created by adding the filtered signal to a copy of the filtered signal shifted by a time unit. A set of correlation signals is created by repeating the process for a range of time units corresponding to a set of sequential sample points. Each correlation signal has a correlation indicator evidencing the strength of the correlation. The correlation signal having the highest correlation strength is identified, and the time shift used to create it is identified as the time of flight of the echo pulse. The echo distance is then calculated based upon the time of flight and the speed of propagation of the echo in the environment. The correlation indicator may the maximum peak value of the correlation signal.

Abstract: An antenna assembly suitable for use with a microwave-based level measurement system mounted on a vessel. The antenna assembly includes an installation thread, a shielded extension, and a rod antenna. The antenna assembly is screwed into a threaded portion in the opening of the vessel. The antenna assembly may be formed as a single integral unit molded from a polymer material. The antenna assembly may also be constructed with the installation thread, the shielded extension and the rod antenna comprising individual polymeric components which are welded together to form a unitary assembly. The polymer material is selected based on chemical resistant properties according to the application.

Abstract: A method for processing echoes in a time-of-flight ranging system or level measurement system. The method comprises an initial noise floor level and identifying potential echoes in an echo signal above the initial noise floor level and a noise signal below the initial noise floor level. One or more portions of the initial noise floor level are modified and an adjusted noise floor level is generated by applying a cubic spline algorithm to the modified portions and the initial noise floor level. The adjusted noise floor level is then used to identify valid echoes in the echo signal and generate an echo signal profile.

Abstract: A method for processing echoes in a time-of-flight ranging system or level measurement system. The method comprises an initial noise floor level and identifying potential echoes in an echo signal above the initial noise floor level and a noise signal below the initial noise floor level. One or more portions of the initial noise floor level are modified and an adjusted noise floor level is generated by applying a cubic spline algorithm to the modified portions and the initial noise floor level. The adjusted noise floor level is then used to identify valid echoes in the echo signal and generate an echo signal profile.

Abstract: An intrinsically safe portable programmer for communicating with the electronic process control equipment over a wireless communication link. The portable programmer comprises a microprocessor controlled electronic circuit housed in an enclosure formed from a polymers polystyrene having a low surface resistivity. The electronic circuit is mounted inside the enclosure with a low voltage battery supply and encased in epoxy to prevent sparking. The electronic circuit includes an infrared transmitter and a keypad. In response to keypad inputs, the electronic circuit generates control signals which are transmitted to the electronic process control equipment via the infrared transmitter.

Abstract: A method and system for echo processing a receive signal using autocorrelation. A receive signal is sampled, digitized and high-pass filtered. A correlation signal is created by adding the filtered signal to a copy of the filtered signal shifted by a time unit. A set of correlation signals is created by repeating the process for a range of time units corresponding to a set of sequential sample points. Each correlation signal has a correlation indicator evidencing the strength of the correlation. The correlation signal having the highest correlation strength is identified, and the time shift used to create it is identified as the time of flight of the echo pulse. The echo distance is then calculated based upon the time of flight and the speed of propagation of the echo in the environment. The correlation indicator may the maximum peak value of the correlation signal.

Abstract: A method and system for high-pass filtering to remove DC and/or low frequency components of a receive signal from the transducer of a level measurement system. In one embodiment, the method includes generating a maximum signal profile and a minimum signal profile for the receive signal, generating a midpoint reference signal from the maximum and minimum signal profiles and subtracting the midpoint reference signal from the receive signal to produce a filtered signal.

Abstract: A housing or enclosure for time of flight ranging systems and/or level measurement devices. The housing comprises an upper lid section and a lower section which are coupled together to form an enclosure for holding a transducer module and electronic circuitry to provide the level measurement funtionality. The housing has an exterior surface which is covered in at least part with a reflective coating. The reflective coating reflects solar radiation and serves to reduce the solar gain and temperature rise variations inside and surrounding the housing. According to another aspect, the reflective coating may also be applied to all or parts of the interior surface.

Abstract: A temperature compensation circuit for a liquid crystal display (LCD) module. The temperature compensation circuit includes a thermistor which in response to changes in temperatures changes the clocking rate for the drive signals for the LCD module. A further bias voltage circuit may be included which in response to a change in temperature changes the bias voltage for the LCD module. The effect of the temperature variable clocking rate and/or bias voltage is to improve the segment contrast and therefore the definition of information displayed on the LCD module. The temperature compensation circuit is particularly suited for LCD modules used in level measurement systems installed in harsh industrial or outdoor environments.

Abstract: A calibration module and methods for a time-of-flight ranging system. The calibration module may be built into the circuitry of the time-of-flight ranging system and allows various operating parameters to be measured and evaluated. The calibration modes include amplitude calibration, frequency calibration, and time delay calibration. The calibration mode also includes an electronic noise measurement mode. The calibration modes may be initiated on power-up or reset, or in response to user input or time-based trigger.

Abstract: A dielectric rod antenna assembly for a level measurement system. The antenna assembly includes a transition structure housed within a coupling sleeve. The transition structure includes a short-circuited waveguide filled with a dielectric material and an exciter element projecting through the waveguide into the material. The transition structure directs electromagnetic energy through the bottom of the dielectric material into a rod antenna attached to the bottom of the coupling sleeve for propagation within the container. The dielectric material includes a longitudinal axial bore having a tapered tip to provide a dielectric-lined waveguide. The bottom end of the dielectric is encircled with a metal ring of a diameter larger than the dielectric to smooth the transition into the rod antenna.

Abstract: A probe for sensing the level of a material or the interface between materials contained in a vessel using Time Domain Reflectometry measurement techniques. The probe comprises a primary conductive rod and at least two secondary conductive rods in spaced relationship with the primary conductive rod for reducing loss of TDR signals propagating through the probe.

Abstract: A probe structure for sensing the level of a liquid or the interface between liquids contained in a vessel using Time Domain Reflectometry measurement technique. The probe comprises a conductive hollow rod and a conductive inner rod in a coaxially spaced relationship inside the hollow rod and extending along the length of the hollow rod. The hollow rod includes perforations along its length to maintain the same liquid level within the probe as that inside the vessel holding the liquid.