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US 4,205,327 AGranted
Two wire current transmitter with adjustable current control linearization
AssigneeRosemount Inc.
InventorCharles J. Dahlke
Life of this patent
Estimating the term…
Abstract
A two wire current transmitter for controlling the total current in the two wires in accordance with a value of a parameter to be sensed, which provides for substantial linearization of the electrical characteristic representative of the value of the parameter to be sensed by adjusting the current from an adjustable current control to substantially compensate for the nonlinear relationship of the parameter to be sensed versus the electrical output of the sensor of said parameter. The circuit also provides for substantial compensation for sensor lead wire effects.
Claims22
A two wire transmitter having two terminals for connection to two wires from a series connected source of DC voltage and a load, the two wire transmitter comprising:
- a voltage regulator means powered solely through said terminals to provide a stable output voltage;
- a sensing circuit including sensor means which is variable as a known nonlinear function of a parameter for providing electrical signals as a function of variation of the sensor means;
- a current source powered by said voltage regulator means solely through said terminals for providing an energizing current to energize said sensing circuit, said current source including linearizing impedance means having an impedance having a predetermined relationship to said known non-linear function, and wherein said energizing current flows through said linearizing impedance means;
- means connected to said sensing circuit and coupled between said two terminals to adjust the current flowing through said two terminals as a function of the electrical signals from said sensing circuit;
- means sensitive to the current flowing through said two terminals to provide a feedback signal to said sensing circuit to cause said electrical signals to tend to return to a known state;
- and
- means for adjusting the energizing current from said current source energizing said sensing circuit as a function of the current flowing through said two terminals to provide a linearizing effect on the relationship between the parameter sensed by the sensor means and the current flowing through said two terminals.
4 more elements
A two wire transducer circuit comprising:
- adjustable current source means including a linearizing impedance means and a controllable impedance means connected in series to provide an energizing current;
- sensor network means connected to said adjustable current source means to receive the energizing current therefrom, said sensor network including sensor means to sense the value of a parameter to provide an unbalanced electrical signal in said sensor network means as a nonlinear function of the parameter to be sensed;
- amplification means coupled to said sensor network means to sense the unbalanced electrical signal in said sensor network means;
- current control means responsive to said amplification means for providing a feedback current to said sensor network means to correct for the sensed electrical unbalance;
- and
- means to provide correction for the nonlinear function of the unbalanced electrical signal relative to the value of the parameter to be sensed, said correction means being connected to said adjustable current source means to change the energizing current flowing through the linearizing impedance means and the controllable impedance means as a function of the feedback current.
3 more elements
A two wire transmitter having two terminals for connection to two wires from a series connected source of DC voltage and a load, the two wire transmitter comprising:
- a voltage regulator means powered solely through said terminals to provide a stable output voltage;
- a sensing circuit including sensor means which is variable as a known nonlinear function of a parameter for providing an electrical signal as a function of variation of the sensor means;
- a current source powered by said voltage regulator means for providing an energizing current to energize said sensing circuit, said current source including linearizing impedance and having an impedance having a predetermined relationship to said known non-linear function, and wherein said energizing current flows through said linearizing impedance means;
- means connected to said sensing circuit and coupled between said two terminals to adjust the current flowing through said two terminals as a function of said electrical signal from said sensing circuit;
- means for providing a first input signal which is a function of said electrical signal provided by the sensing circuit;
- span adjusting means for providing a second input signal which is independent of said electrical signal, said second input signal being adjustable for different desired spans;
- and
- means for adjusting the energizing current from said current source energizing said sensing circuit as a function of the first and second input signals to provide a linearizing effect on the relationship between the parameter sensed by the sensor means and the current flowing through said two terminals.
5 more elements
A two wire transducer circuit comprising:
- adjustable current source means including a linearizing impedance means and a controllable impedance means connected in series to provide an energizing current;
- sensor network means connected to said adjustable current source means to receive the energizing current therefrom, said sensor network including sensor means to sense the value of a parameter to provide an unbalanced electrical signal in said sensor network means as a nonlinear function of the parameter to be sensed;
- means for providing an input signal which is a function of said unbalanced electrical signal;
- span adjusting means for providing a span reference signal which is independent of said unbalanced electrical signal, the span adjusting means permitting adjustment of the span reference signal to thereby adjust output span of the two wire transducer circuit;
- and
- means to provide correction for the nonlinear function of the unbalanced electrical signal relative to the value of the parameter to be sensed, said correction means being connected to said adjustable current source means to change the energizing current flowing through the linearizing impedance means and the controllable impedance means as a function of the input signal and the span reference signal.
3 more elements
Dependencies are inferred from the claim text.