Transmitter with improved compensation
First Claim
1. A measurement transmitter, comprising:
- conversion means for sensing a process variable related to pressure within a span of process variable values and for providing a digitized output representative of the sensed pressure process variable;
a memory for storing at least two membership functions, each membership function having a non-zero value over a predetermined region of the process variable span and a substantially zero value over the remainder of the span, and for storing a set of compensation formulas, each formula corresponding to a membership function;
selection means for selecting those membership functions which have a non-zero value at the digitized process variable;
correction means for providing at least one correction value, each correction value calculated from a compensation formula corresponding to a selected membership function;
weighting means for weighting each correction value by its corresponding selected membership function, and for combining the weighted correction values to provide a compensated process variable;
an output circuit for coupling the compensated process variable to a control circuit; and
wherein there are at least three membership functions for the pressure process variable, the membership functions each having a center point corresponding to a maximum value of the membership function, where the center points are evenly spaced along the span of process variable values.
1 Assignment
0 Petitions
Accused Products
Abstract
A circuit for compensating variables in a measurement transmitter. Within the transmitter, a sensor senses a primary process variable such as differential pressure and a converter digitizes the sensed process variable. The sensor senses pressures within a span of pressures values. A memory inside the transmitter stores at least two membership functions, each membership function having a non-zero value over a predetermined region of the process variable span and a substantially zero value over the remainder of the span. The memory also stores a set of compensation formulas, each formula corresponding to a membership function. A selection circuit in the transmitter selects those membership functions which have a non-zero value at the digitized process variable and a correction circuit provides at least one correction value, each correction value calculated from a compensation formula corresponding to a selected membership function. A weighting circuit multiplies each correction value by its corresponding selected membership function, and combines the multiplicands to provide a compensated process variable. The compensated process variable is coupled to a control circuit connecting the transmitter to a control system.
-
Citations
96 Claims
-
1. A measurement transmitter, comprising:
-
conversion means for sensing a process variable related to pressure within a span of process variable values and for providing a digitized output representative of the sensed pressure process variable; a memory for storing at least two membership functions, each membership function having a non-zero value over a predetermined region of the process variable span and a substantially zero value over the remainder of the span, and for storing a set of compensation formulas, each formula corresponding to a membership function; selection means for selecting those membership functions which have a non-zero value at the digitized process variable; correction means for providing at least one correction value, each correction value calculated from a compensation formula corresponding to a selected membership function; weighting means for weighting each correction value by its corresponding selected membership function, and for combining the weighted correction values to provide a compensated process variable; an output circuit for coupling the compensated process variable to a control circuit; and wherein there are at least three membership functions for the pressure process variable, the membership functions each having a center point corresponding to a maximum value of the membership function, where the center points are evenly spaced along the span of process variable values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
-
-
19. A transmitter in a process control system comprising:
-
a sensor for sensing a physical variable in the system, the physical variable taking on values within a span of values, the sensor having an output representative of the physical variable within the span; digitizing means for digitizing the sensor output; selection and storing means for selecting a region from a set of regions in a different portion of the span, a region becoming selected when the sensor output is included within the region, each region having a compensation formula and a membership function corresponding thereto; computation means for retrieving the membership functions and the compensation formulas corresponding to the selected regions, and for providing the ordinates of the membership functions at the value of the sensor output and for providing the value of the compensation formulas at the value of the sensor output; and compensation means for weighting the value of the compensation formulas by the ordinate of the corresponding membership functions so as to provide a compensated transmitter output. - View Dependent Claims (20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
-
-
23. The transmitter of claim 23 where current in the loop has a magnitude representative of the compensated physical variable.
-
43. A measurement transmitter, comprising:
-
conversion means for sensing a process variable related to temperature within a span of process variable values and for providing a digitized output representative of the sensed process variable; a memory for storing at least two membership functions, each membership function having a non-zero value over a predetermined region of the process variable span and a substantially zero value over the remainder of the span, and for storing a set of compensation formulas, each formula corresponding to a membership function; selection means for selecting those membership functions which have a non-zero value at the digitized process variable; correction means for providing at least one correction value, each correction value calculated from a compensation formula corresponding to a selected membership function; weighting means for weighting each correction value by its corresponding selected membership function, and for combining the weighted correction values to provide a compensated process variable; an output circuit for coupling the compensated process variable to a control circuit; and wherein there are three membership functions for the temperature process variable, the membership functions each having a center point corresponding to a maximum value of the membership function, where the center points are evenly spaced along the span of process variable values. - View Dependent Claims (44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60)
-
-
61. A measurement transmitter, comprising:
-
conversion meads for sensing a flow process variable within a span of process variable values and for providing a digitized output representative of the sensed process variable; a memory for storing at least two membership functions, each membership function having a non-zero value over a predetermined region of the flow process variable span and a substantially zero value over the remainder of the span, and for storing a set of compensation formulas, each formula corresponding to a membership function; selection means for selecting those membership functions which have a non-zero value at the digitized process variable; correction means for providing at least one correction value, each correction value calculated from a compensation formula corresponding to a selected membership function; weighting means for weighting each correction value by its corresponding selected membership function, and for combining the weighted correction values to provide a compensated process variable; an output circuit for coupling the compensated process variable to a control circuit; and wherein there are three membership functions for the flow process variable, the membership functions each having a center point corresponding to a maximum value of the membership function, where the center points are evenly spaced along the span of process variable values. - View Dependent Claims (62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78)
-
-
79. A measurement transmitter, comprising:
-
conversion means for sensing a level process variable within a span of process variable values and for providing a digitized output representative of the sensed process variable; a memory for storing at least two membership functions, each membership function having a non-zero value over a predetermined region of the level process variable span and a substantially zero value over the remainder of the span, and for storing a set of compensation formulas, each formula corresponding to a membership function; selection means for selecting those membership functions which have a non-zero value at the digitized process variable; correction means for providing at least one correction value, each correction value calculated from a compensation formula corresponding to a selected membership function; weighting means for weighting each correction value by its corresponding selected membership function, and for combining the weighted correction values to provide a compensated process variable; an output circuit for coupling the compensated process variable to a control circuit; and wherein there are three membership functions for the level process variable, the membership functions each having a center point corresponding to a maximum value of the membership function, where the center points are evenly spaced along the span of process variable values. - View Dependent Claims (80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96)
-
Specification