The Babcock & Wilcox Company

Jane E Smith

John W Robertson, Jr

Eugene Skuratovsky

James K Knudsen

Victor J Budan

Rowland E Whitford

David J Wroblewski

Raymond J Sampson

Thomas B DeWitt

A method and apparatus for processing optically generated signals to form a two-wire 4-20 mA signal comprises generating a control signal having pulses at a selected frequency to drive a light emitter which generates light pulses, transmitting the light pulses to a light detector over a transmission line having variable attenuation to form a sensor signal and amplifying the sensor signal in an operational amplifier. The variations and attentuations follow a process variable to be measured. To save power the operational amplifier has a low-current mode into which it is switched whenever no pulse is present in the sensor signal. The amplifier is switched into its high-current mode only when a pulse is present in the sensor signal. Switching is controlled by the control signal for the light emitter. Peaks in the signal from the operations amplifier are sampled and held and then subject to low pass filtering to remove the selected frequency componnent and leave a cyclic filtered signal. The operational amplifier also receives a signal to drive it toward ground using a feedback clamping signal which changes slowly with respect to the cyclic filter signal. The filter signal is used to trigger a multivibrator to form a pulse signal having pulses with fixed length and amplitude for each cycle of the filter. The pulse signal is then averaged with respect to its voltage and subjected to zero and span adjustments. The voltage signal is then converted to a two-line 4-20 mA current signal.

Two-wire 4-20 mA electronics for a fiber optic vortex shedding flowmeter

A position transmitter which can be incorporated in a pneumatic-pneumatic or electro-pneumatic converter, and which readily provides for calibration between a zero position and a maximum position of a device to be actuated by the converter. The invention also provides a virtually non-interacting zero and span or full scale adjustment, for ease of calibration.

Position transmitter for a pneumatic-pneumatic or electro-pneumatic

A sensor arrangement for a vortex shedding flowmeter having a flowmeter housing which is exposed to a flowing fluid in a fluid space on one side of the housing, comprises a sensor housing which is connected to the flowmeter housing and which defines an internal sensor space. A sensor beam is connected to the housing and has a first portion extending into the sensor space with a second portion extending through the flowmeter housing into the fluid space. A diaphragm resiliently carries the beam for movement in response to the passage of vortices in the fluid space. A mounting bracket is detachably connected to the sensor housing and carries a sensor element. The sensor element is operatively connected to the first portion of the sensor beam and can be easily engaged and disengaged thereto when the mounting bracket is to be removed. In this way if the sensor element fails, it can be replaced without stopping the flow of fluid or disturbing the sensor beam.

On-line replacement sensor assembly for a vortex shedding flowmeter

A resistive network is used for an electro-pneumatic converter so that the speed of the electro-pneumatic converter can be regulated. The converter includes a reversible DC servo motor having a pair of terminals connected to a pair of lines. The lines are selectively connectable to a common terminal of a power supply. The power terminal of the power supply is connected over a variable resistor to a terminal connecting the lines. Selectively connecting one of the lines to the common terminal causes electrical power to pass through the motor and one for an opposite direction to turn the motor shaft in a selected direction of rotation. The speed of rotation is determined by the position of the variable resistor. The motor shaft is used in conjunction with a cam that is associated with a nozzle supplied with pressurized gas over a bellows. The nozzle is moved closer or further away from the cam edge as the bellows expands or contracts. A line connected upstream of the bellows provides gas at a selected pressure which is porportional to the position of the cam. The position of the cam is determined by the rotation of the motor shaft.

Variable speed resistive network for a pneumatic servo assembly of an

An electro-pneumatic control system (10) is provided having closed loop control of a D.C. motor (12) which is operated from a biased motor servo circuit (14) thereby eliminating the need for a negative power supply to provide bi-directional rotation. Closed loop control is provided by a feedback signal from a pressure transducer (26) monitoring the pressure output signal (22) of the mechanical servo assembly (20).

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Mentor, OH, United States of America

Jane E Smith