Measuring and testing – Volume or rate of flow – Using differential pressure
Reexamination Certificate
1998-01-13
2001-07-03
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Volume or rate of flow
Using differential pressure
Reexamination Certificate
active
06253624
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to transmitters for process control. In particular, the present invention relates to pressure transmitters which measure flow.
In process control, fluid movement through pipes is monitored by a series of process control transmitters connected to the pipes. The transmitters contain sensors that sense the difference between two pressures in a pipe (i.e. a differential pressure). From the differential pressure measurement, these transmitters infer the mass flow rate of the fluid in the pipe.
Generally, transmitters sense the differential pressure across an obstruction in the pipe. A typical obstruction is an orifice plate, which is a perforated disk inserted into the pipe. Although such disks provide a large and easily sensed pressure drop, they complicate the mass flow rate calculation because a number of compensation factors must be added to the calculation to account for fluid flow disruptions created by the disk. The disks also cause a substantial loss in pressure in the pipe. This reduction in pressure constitutes a needless and costly waste of energy.
SUMMARY OF THE INVENTION
A pressure transmitter produces signals indicative of a flow in a pipe. The transmitter has a pressure sensor that is fluidly coupled to two ports in the pipe, and the pipe has a substantially constant cross-section between the two ports. Aspects of the invention include a circuit coupled to the pressure sensor that produces a digital value related to the fluid flow as a function of the pressure difference between the two ports.
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Broden David A.
Wiklund David E.
Fuller Benjamin R.
Magee Theodore M.
Rosemount Inc.
Thompson Jewel
Westman Champlin & Kelly P.A.
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