Flow measurement compensation technique for use with an averaging pitot tube type primary element
First Claim
1. A transmitter for coupling to an averaging pitot tube type primary element introduced into a pipe through a single opening in the pipe having a generally forward facing tube and a second tube, the transmitter calculating flow rate (Q) of process fluid and comprising:
- a total pressure sensor for sensing total pressure (PTOT) of the process fluid using the generally forward facing tube;
a differential pressure sensor for sensing a differential pressure (h) in the process fluid between the generally forward facing tube and the second tube;
circuitry which calculates flow rate (Q) based upon the total pressure (PTOT) the differential pressure (h), fluid density (ρ
), and the gas expansion factor (Y1) wherein fluid density (ρ
) and the gas expansion factor (Y1) are calculated as a function of the total pressure (PTOT) and differential pressure (h) ; and
I/O circuitry for coupling to a process control loop and transmitting the calculated flow rate (Q).
1 Assignment
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Accused Products
Abstract
A transmitter in a process control system for measuring flow rate measures total pressure (PTOT) and differential pressure (h) of process fluid flowing through a process pipe. The static pressure (PSTAT) is determined based upon the total pressure (PTOT). The calculated static pressure is used to determine the fluid density (ρ) and the gas expansion factor (Y1) of the process fluid flowing in the pipe. This information is used to calculate flow rate (Q) of the process fluid.
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Citations
18 Claims
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1. A transmitter for coupling to an averaging pitot tube type primary element introduced into a pipe through a single opening in the pipe having a generally forward facing tube and a second tube, the transmitter calculating flow rate (Q) of process fluid and comprising:
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a total pressure sensor for sensing total pressure (PTOT) of the process fluid using the generally forward facing tube; a differential pressure sensor for sensing a differential pressure (h) in the process fluid between the generally forward facing tube and the second tube; circuitry which calculates flow rate (Q) based upon the total pressure (PTOT) the differential pressure (h), fluid density (ρ
), and the gas expansion factor (Y1) wherein fluid density (ρ
) and the gas expansion factor (Y1) are calculated as a function of the total pressure (PTOT) and differential pressure (h) ; andI/O circuitry for coupling to a process control loop and transmitting the calculated flow rate (Q). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for use in a transmitter of determining flow (Q) of a process fluid, comprising:
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introducing an averaging pitot tube type primary element into a single opening in the pipe, the pitot tube having a generally forward facing tube and a second tube; sensing a total pressure (PTOT) generated by the forward facing tube of the averaging pitot tube type primary element; sensing a differential pressure (h) generated by the second tube of the averaging pitot tube type element; and calculating flow rate (Q) based upon static pressure (PSTAT), total pressure (PTOT) and differential pressure (h) , wherein static pressure (PSTAT) is determined based upon total pressure (PTOT) and differential. pressure (h). - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification