Invensys Systems, Inc.

The Foxboro Company

David W Clarke

Manus Patrick Henry

James H Vignos

Tarek Ghaoud

Wade M Mattar

David J Sandoz

Janice Yang

Justin Peter Lowe

A control and measurement system for a coriolis flowmeter having a flowtube, a driver adapted to vibrate the flowtube, and a pair of sensors adapted to generate signals indicative of movement of the flowtube when it is being vibrated by the driver, wherein the sensors are positioned relative to one another so the signals from the sensors are indicative of a mass flow rate of fluid through the flowtube. A digital drive signal generator is adapted to generate a variable digital drive signal for controlling operation of the driver. The digital drive signal generator can be adapted to cause the driver to resist motion of the flowtube during a first time period and amplify motion of the flowtube during a second time period. The digital drive signal generator can also be adapted to initiate motion of the flowtube by sending one or more square wave signals to the driver.

Digital flowmeter

A controller for a flowmeter includes an input module operable to receive a sensor signal from a sensor connected to a vibratable flowtube. The sensor signal is related to a fluid flow through the flowtube. The controller also includes a signal processing system operable to receive the sensor signal, determine sensor signal characteristics, and output drive signal characteristics for a drive signal applied to the flowtube. An output module is operable to output the drive signal to the flowtube and a control system is operable to modify the drive signal and thereby maintain oscillation of the flowtube during a transition of the flowtube from a substantially empty state to a substantially full state.

A process variable transmitter, implemented in a dual PLL structure, includes a first PLL having a first bandwidth producing a first output signal, and a second PLL having a second bandwidth narrower than the first bandwidth of the first PLL. The first and second PLLs are operable to lock into a frequency of an input signal and produce first and second output signals, respectively. The second PLL is operable to lock into the frequency of the input signal with greater accuracy and greater immunity to noise than the first PLL. A switch is operable to switch an output signal of the process variable transmitter between the first output signal and the second output signal.

Vortex flowmeter

A flowmeter includes a vibratable conduit, a driver connected to the conduit and operable to impart motion to the conduit, and a sensor connected to the conduit and operable to sense the motion of the conduit. A control and measurement system is connected to the driver and the sensor. The control and measurement system includes circuitry to receive a sensor signal from the sensor, generate a drive signal based on the sensor signal, supply the drive signal to the driver, and generate a measurement of a property of material flowing through the conduit based on the sensor signal.

A signal processor, for use with a zero crossing module of a vortex flow meter, includes a peak amplitude detector, a comparator, and a filter module. The filter module is enabled when the comparator determines that the amplitude is less than a low flow rate threshold. The filter module filters a vortex signal and the filtered signal is provided to a frequency estimator that uses a zero crossing algorithm. The signal processor may increase the signal-to-noise ratio at low flow rates for which the frequency estimator may not otherwise be able to accurately estimate the flow rate. Low flow rates may be measured by determining that there is a low flow rate using amplitude detection of a vortex signal, filtering the vortex signal based on the amplitude detection, and using a zero crossing algorithm on the filtered vortex signal.

Evaluating a vortex flow-meter signal

Self-validating (SEVA) sensors implemented in a control process provide various metrics regarding sensed variables to a central control unit. Specifically, SEVA sensors provide measurements of the variables and validity information about the measurements, which may include fault information about the sensors themselves. A control unit utilizes the various SEVA metrics even when large numbers of SEVA sensors are used, a situation that is otherwise problematic due to difficulties in assimilating data from multiple SEVA sensors. Accordingly, the control unit distinguishes sensor faults from actual process changes, and responds as needed, even when large numbers of SEVA sensors are implemented together. Specifically, the monitoring and control unit assimilates signals from multiple SEVA sensors using a multi-variate statistical analysis, and compares results of this analysis with a model characterizing behavior of the process (where the model may take into account actuator position information) and/or historical statistical data.

Process monitoring and control using self-validating sensors

A digital flowmeter includes a vibratable conduit, a driver connected to the conduit and operable to impart motion to the conduit, and a sensor connected to the conduit and operable to sense the motion of the conduit. A control and measurement system is connected to the driver and the sensor. The control and measurement system includes circuitry to receive a sensor signal from the sensor, generate a drive signal based on the sensor signal using digital signal processing, supply the drive signal to the driver, and generate a measurement of a property of a two-phase material flowing through the conduit based on the signal from the sensor.

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Oxford, United Kingdom

David W Clarke