Analog transducer circuit with digital control
First Claim
1. A transmitter for providing an analog output signal representative of a sensed parameter and representative of an input adjustment signal, comprising:
- digital means coupled to receive the input adjustment signal for calculating and providing a control signal representative of an adjustment to the analog output signal;
analog means responsive to the sensed parameter for providing the analog output signal as a continuous function of the sensed parameter; and
control means coupled to the analog means and controlled by the control signal for controlling adjustment of the analog output signal by the analog means such that continuity of the analog output signal is undisturbed by calculation in the digital means.
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Abstract
A two wire transmitter controls loop current as a function of a sensed parameter such as pressure or temperature using analog sensing and signal processing circuitry. Corrections, such as for zero, span, and linearity are provided in the form of analog correction signals by a digital circuit which includes nonvolatile memory, a microcomputer, and a digital-to-analog (D/A) converter. The microprocessor controls the D/A converter as a function of stored digital correction values to produce the analog correction signals used by the analog signal processing circuitry to control the magnitude of the loop current flowing through the two wire transmitter.
83 Citations
36 Claims
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1. A transmitter for providing an analog output signal representative of a sensed parameter and representative of an input adjustment signal, comprising:
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digital means coupled to receive the input adjustment signal for calculating and providing a control signal representative of an adjustment to the analog output signal; analog means responsive to the sensed parameter for providing the analog output signal as a continuous function of the sensed parameter; and control means coupled to the analog means and controlled by the control signal for controlling adjustment of the analog output signal by the analog means such that continuity of the analog output signal is undisturbed by calculation in the digital means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A transmitter for providing an analog output signal representative of a sensed parameter and representative of an input signal for controlling transmitter adjustment, comprising:
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digital means coupled to receive the input signal for calculating and providing a digital control signal representative of the adjustment; converter means coupled to the digital means for converting the digital control signal to a converter signal having a duty cycle representative of the adjustment; switch means coupled to the converter means for controlling switching as a function of the converter signal; sensor means responsive to the sensed parameter for providing an analog sensor signal to the switch means; and output means coupled to the switch means for providing the analog output signal as a function of the analog sensor signal and the converter signal. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A two wire transmitter for connection in a current loop to control a loop current flowing in the loop as a function of a sensed parameter, the transmitter being powered by the loop current, the transmitter comprising:
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sensing means responsive to the sensed parameter for producing an analog sensor signal which varies as a function of the sensed parameter; storage means for storing digital correction values;
converting means coupled to the storage means for converting the digital correction values to analog correction signals; andanalog output means coupled to the sensing means and the converting means for controlling the magnitude of the loop current as a function of the analog sensor signal and the analog correction signals. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A transmitter for providing an analog output signal representative of a sensed parameter and corrected as a function of digital transmitter adjustment values;
- the transmitter comprising;
sensing means responsive to the sensed parameter for producing an analog sensor signal which varies as a function of the sensed parameter; converting means responsive to the digital transmitter adjustment values for converting the digital transmitter adjustment values to analog correction signals; and analog output means coupled to the sensing means and the converting means for providing the analog output signal as a function of the analog sensor signal and the analog correction signals.
- the transmitter comprising;
Specification