Abstract: A loop powered process instrument comprises a control system measuring a process variable and developing a measurement signal representing the process variable. A two-wire circuit, for connection to a remote power source using a two-wire process loop, controls current on the loop in accordance with the measurement signal. A power supply with galvanic isolation is connected to the two-wire circuit and the control system to isolate the two-wire circuit from the control system. The power supply receives power from the two-wire process loop and supplies power to the control system. The power supply comprises a voltage regulator receiving loop power and developing a regulated output voltage. A current switching circuit receives the regulated output voltage and drives a primary of a transformer. A secondary of the transformer is coupled to the control system. A voltage shift control includes an isolator circuit driven by the control system for controlling voltage supplied by the voltage regulator.

Abstract: A loop powered process instrument comprises a control system measuring a process variable and developing a measurement signal representing the process variable. A two-wire circuit, for connection to a remote power source using a two-wire process loop, controls current on the loop in accordance with the measurement signal. A power supply with galvanic isolation is connected to the two-wire circuit and the control system to isolate the two-wire circuit from the control system. The power supply receives power from the two-wire process loop and supplies power to the control system. The power supply comprises a voltage regulator receiving loop power and developing a regulated output voltage. A current switching circuit receives the regulated output voltage and drives a primary of a transformer. A secondary of the transformer is coupled to the control system. A voltage shift control includes an isolator circuit driven by the control system for controlling voltage supplied by the voltage regulator.

Abstract: A loop powered process instrument comprises a control system including a control circuit, a modem circuit and a loop output circuit. The control circuit measures a process variable and develops a measurement signal representing the process variable and includes a loop control circuit and a communication circuit. The modem circuit is operatively connected to the communication circuit and includes a modulation input port and a modulation output port. The loop output circuit receives a measurement signal from the loop control circuit and is connected to the modulation input port. A two-wire circuit is for connection to a remote power source using a two-wire process loop. A power supply with isolation is connected to the two-wire circuit and the loop output circuit to isolate the two-wire circuit from the control system.

Abstract: A loop powered process instrument comprises a control system including a control circuit, a modem circuit and a loop output circuit. The control circuit measures a process variable and develops a measurement signal representing the process variable and includes a loop control circuit and a communication circuit. The modem circuit is operatively connected to the communication circuit and includes a modulation input port and a modulation output port. The loop output circuit receives a measurement signal from the loop control circuit and is connected to the modulation input port. A two-wire circuit is for connection to a remote power source using a two-wire process loop. A power supply with isolation is connected to the two-wire circuit and the loop output circuit to isolate the two-wire circuit from the control system.

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 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 process measurement instrument including a fiducial and adapted for detection of the fiducial. The instrument comprises 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 signal processing circuit is operatively coupled to the interface circuit for receiving the analog receive signal and determining characteristics of reflected echoes for the fiducial and the target of interest. The controller is operatively coupled to the signal processing circuit and includes a diagnostic routine responsive to the characteristics of the reflected echo for the fiducial in determining if a fiducial error condition exists.

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 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.