Abstract: A level measurement instrument comprises an analog circuit for transmitting a pulse signal at a target of interest and receiving reflected echoes of the pulse signal and developing an echo waveform representative of the reflected echoes. A programmed digital circuit is operatively coupled to the analog circuit and comprises a programmed controller and memory. The controller is operatively programmed to identify peaks in the echo waveform and store an active peak list in the memory from a current measurement scan and a buffer peak list from prior measurement scans. The controller is further programmed to match peaks in the active peak list to peaks in the buffer peak list, to select a target peak from the active peak list based on which of the matched peaks have moved, and determining material level responsive to the target peak.

Abstract: A level measurement instrument comprises an analog circuit for transmitting a pulse signal at a target of interest and receiving reflected echoes of the pulse signal and developing an echo waveform representative of the reflected echoes. A programmed digital circuit is operatively coupled to the analog circuit and comprises a programmed controller and memory. The controller is operatively programmed to identify peaks in the echo waveform and store an active peak list in the memory from a current measurement scan and a buffer peak list from prior measurement scans. The controller is further programmed to match peaks in the active peak list to peaks in the buffer peak list, to select a target peak from the active peak list based on which of the matched peaks have moved, and determining material level responsive to the target peak.

Abstract: There is disclosed herein a method of measuring and profiling a process liquid in a process vessel. The process liquid includes an emulsion layer between two media of differing dielectric constants. An electromagnetic signal is generated and transmitted along a probe, defining a transmission line, extending into the vessel. The transmission line comprises a conductor in contact with the process liquid with an insulating coating on the conductor to maximize signal penetration in the process liquid. A reflected signal is received from the transmission line and a programmed controller is operatively connected to the probe for measuring characteristics of reflected signal energy along the transmission line for profiling the emulsion layer.

Abstract: A process measurement instrument includes a fiducial and is adapted for detection of the fiducial. The instrument includes an interface circuit comprising a drive circuit for transmitting a pulse signal at the fiducial and at a target of interest and a receive circuit receiving reflected echoes of the pulse signal and developing an analog receive signal representative of the reflected echoes. A processing circuit is operatively coupled to the interface circuit for receiving the analog receive signal and comprising a threshold detector detecting if the analog receive signal is above a select threshold value. A controller is operatively coupled to the processing circuit and responsive to leading and trailing edges of the reflected echo for the fiducial and determining an average of the leading and trailing edges to determine location of the fiducial.

Abstract: A probe for use with a measurement instrument includes a circuit connected to the probe. The probe comprises a process adaptor for mounting to a process vessel and including a through bore extending from a connector end to a process end. A counterbore at the connector end defines a shoulder. A support assembly is received in the counterbore and rests on the shoulder. The support assembly comprises an annular rod support having a through opening with a tension rod extending through the opening and secured at opposite sides of the annular rod support. A locking nut secures the support assembly in the counterbore to maintain the annular rod support in compression. A probe rod extends from a process end of the tension rod. A seal assembly is operatively secured to the process adaptor at the connector end with the seal pin in electrical contact with a connector end of the tension rod.

Abstract: A guided wave radar level measurement instrument comprises a probe defining a transmission line for sensing material level. A probe interface circuit is connected to the probe for generating pulses on the transmission line and receiving reflected signals from the transmission line. The probe interface circuit comprises a transmit pulse generator for generating a transmit pulse, a sample pulse generator for generating a sample pulse, and a delay lock loop for controlling the transmit and sample pulse generators. The delay lock loop is controlled by a pulse repetition frequency having a duty cycle less than 50%.

Abstract: A through air level measurement instrument for use in minimizing tank rattle comprises a housing and an antenna secured to the housing. A process adaptor is associated with the antenna and the housing for securing the instrument to a closed tank with the antenna directed into an interior of the closed tank. A control in the housing generates and receives a high frequency signal using an electromagnetic radiating element proximate the antenna. The control comprises an equivalent time sampling circuit including a main oscillator driving a timing circuit controlling timing between transmitted and sample pulses. A noise generator is operatively associated with the main oscillator to randomly modulate timing of the main oscillator. The control minimizes inaccuracies caused by tank rattle.

Abstract: An ultrasonic point level measurement instrument comprises a measurement circuit and a transducer. The transducer transmits and receives acoustic signals under control of the measurement circuit. An improvement in the transducer comprises a transducer housing including a pair of spaced apart legs to define a gap therebetween. Each leg includes an interior cavity. A pair of crystal assemblies each comprise a crystal mounted to a circuit board. The circuit board includes conduction paths for connection between the crystal and a terminal pad. Each crystal assembly is received in the interior cavity of one of the legs with the circuit board spacing the crystal from walls of the leg. A pair of cables are each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.

Abstract: A magnetostrictive level sensing instrument is used for sensing level in a process vessel and comprises an elongate tube having a near end and a distal end. A magnet is selectively positionable proximate the tube responsive to level of the processed material. A magnetostrictive wire in the tube has first and second ends. The second end is operatively secured at the tube distal end. A pair of shear mode crystals are mounted proximate the tube near end. The crystals sandwich the magnetostrictive wire proximate the first end. A sensing circuit is operatively connected to the magnetostrictive wire and the pair of crystals for generating an electrical pulse on the magnetostrictive wire whereby a magnetic field produced by the magnet interacts with the electrical pulse to produce a torsional wave on the magnetostrictive wire sensed by the pair of crystals.

Abstract: A loop powered process instrument comprises a control circuit measuring a process variable and developing a control signal representing the process variable. An output circuit for connection to a two-wire process loop controls current on the loop in accordance with the control signal. A power supply circuit is connected to the output circuit and the control circuit for receiving power from the two-wire process loop and supplying power to the control circuit. The power supply comprises cascaded charge pump circuits.

Abstract: A process control instrument includes a circuit board having a control circuit for generating or receiving a high frequency signal. An antenna includes an electrical conductor. An intrinsic safety circuit couples the control circuit to the antenna and comprises a microstrip transmission line on the circuit board electrically connecting the control circuit to the electrical conductor. A safety stub has a first end electrically connected to the transmission line proximate the electrical conductor and a second end connected to a ground of the control circuit.

Abstract: A process control instrument comprises a control for generating or receiving a high frequency signal. A waveguide comprises a cylindrical housing closed at one end by a rear wall. A loop launcher is operatively connected to the control and comprises a wire having a first straight leg electrically connected at one end to the control and extending into the waveguide a first select length. A second straight leg is connected at one end to the rear wall and extends into the waveguide a second select length, greater than the first select length. A curved middle section connects the other ends of the first and second straight legs. An antenna is operatively coupled to the waveguide.

Abstract: A process control instrument comprises a control for generating or receiving a high frequency signal. A waveguide comprises a cylindrical housing closed at one end by a rear wall. A loop launcher is operatively connected to the control and comprises a wire having a first straight leg electrically connected at one end to the control and extending into the waveguide a first select length. A second straight leg is connected at one end to the rear wall and extends into the waveguide a second select length, greater than the first select length. A curved middle section connects the other ends of the first and second straight legs. An antenna is operatively coupled to the waveguide.

Abstract: A process control instrument includes a circuit board having a control circuit for generating or receiving a high frequency signal. An antenna includes an electrical conductor. An intrinsic safety circuit couples the control circuit to the antenna and comprises a microstrip transmission line on the circuit board electrically connecting the control circuit to the electrical conductor. A safety stub has a first end electrically connected to the transmission line proximate the electrical conductor and a second end connected to a ground of the control circuit.

Abstract: A guided wave radar measurement instrument comprises a probe defining a guided wave radar transmission line. A pulse circuit is connected to the probe for generating a very fast stream of pulses on the transmission line and receiving reflected pulses returned on the transmission line. The reflected pulses represent a characteristic of a material being measured. An equivalent time sampling circuit is connected to the pulse circuit operable to sample reflected pulses to build a time multiplied picture of the reflected pulses and comprises a ramp generator circuit generating a saw tooth ramp signal used to selectively delay sampling reflected pulses to build the time multiplied picture. In one aspect of the instrument, the saw tooth ramp signal has a controlled ramp start for each cycle and retrace at an end of the cycle.

Abstract: A guided wave radar measurement instrument comprises a probe defining a guided wave radar transmission line. A pulse circuit is connected to the probe for generating a very fast stream of pulses on the transmission line and receiving reflected pulses returned on the transmission line. The reflected pulses represent a characteristic of a material being measured. An equivalent time sampling circuit is connected to the pulse circuit operable to sample reflected pulses to build a time multiplied picture of the reflected pulses and comprises a ramp generator circuit generating a saw tooth ramp signal used to selectively delay sampling reflected pulses to build the time multiplied picture. In one aspect of the instrument, the saw tooth ramp signal has a controlled ramp start for each cycle and retrace at an end of the cycle.

Abstract: A guided wave radar measurement instrument comprises a probe defining a guided wave radar transmission line. A pulse circuit is connected to the probe for generating a very fast stream of pulses on the transmission line and receiving reflected pulses returned on the transmission line. The reflected pulses represent a characteristic of a material being measured. An equivalent time sampling circuit is connected to the pulse circuit operable to sample reflected pulses to build a time multiplied picture of the reflected pulses and comprises a ramp generator circuit generating a saw tooth ramp signal used to selectively delay sampling reflected pulses to build the time multiplied picture. In one aspect of the instrument, the saw tooth ramp signal has a controlled ramp start for each cycle and retrace at an end of the cycle.

Abstract: A guided wave radar measurement instrument comprises a probe defining a guided wave radar transmission line. A pulse circuit is connected to the probe for generating a very fast stream of pulses on the transmission line and receiving reflected pulses returned on the transmission line. The reflected pulses represent a characteristic of a material being measured. An equivalent time sampling circuit is connected to the pulse circuit operable to sample reflected pulses to build a time multiplied picture of the reflected pulses and comprises a ramp generator circuit generating a saw tooth ramp signal used to selectively delay sampling reflected pulses to build the time multiplied picture. In one aspect of the instrument, the saw tooth ramp signal has a controlled ramp start for each cycle and retrace at an end of the cycle.

Abstract: A time domain reflectometry measuring instrument uses a microprocessor that provides added functionality and capabilities. The circuit electronics and probe are tested and calibrated at the factory. Installation and commissioning by the user is simple. The user installs the probe. The transmitter is attached to the probe. The user connects a standard shielded twisted pair to the electronics. Power is applied and the device immediately displays levels. A few-simple parameters may need to be entered such as output characteristics and the process material dielectric constant.

Abstract: A time domain reflectometry measuring instrument uses a microprocessor that provides added functionality and capabilities. The circuit electronics and probe are tested and calibrated at the factory. Installation and commissioning by the user is simple. The user installs the probe. The transmitter is attached to the probe. The user connects a standard shielded twisted pair to the electronics. Power is applied and the device immediately displays levels. A few simple parameters may need to be entered such as output characteristics and the process material dielectric constant.