US4783659A — Analog transducer circuit with digital control

Claim 1

Independent Claim 109 words

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.

Claim 2

Dependent Claim 109 words

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.

Claim 3

Dependent Claim 34 words

The transmitter of claim 1 wherein the digital means calculates the control signal at a first rate and the analog means provides the output signal at a second rate independent of the first rate.

Claim 4

Dependent Claim 23 words

The transmitter of claim 2 wherein the output signal is free of aliasing between variation of the sensed parameter and the first rate.

Claim 5

Dependent Claim 22 words

The transmitter of claim 1 wherein the control means comprises switch means controlled by the control signal for controlling the analog means.

Claim 6

Dependent Claim 21 words

The transmitter of claim 4 wherein the control means comprises a digital-to-analog converter coupled to control actuation of the switch means.

Claim 7

Dependent Claim 20 words

The transmitter of claim 5 wherein the digital-to-analog converter provides a pulse width modulated control signal to the switch means.

Claim 8

Dependent Claim 37 words

The transmitter of claim 6 wherein the pulse width modulated control signal is modulated at a high enough modulation rate such that an output rate of the analog output signal is not limited by the modulation rate.

Claim 9

Dependent Claim 23 words

The transmitter of claim 7 wherein the analog means comprises integrator means coupled to the switch means for damping the analog output signal.

Claim 10

Dependent Claim 16 words

The transmitter of claim 8 wherein the control signal is representative of a desired span adjustment.

Claim 11

Dependent Claim 16 words

The transmitter of claim 8 wherein the control signal is representative of a desired zero adjustment.

Claim 12

Dependent Claim 16 words

The transmitter of claim 8 wherein the transmitter is coupled to an energized by a loop.

Claim 13

Dependent Claim 17 words

The transmitter of claim 8 wherein the analog output signal is a 4 to 20 milliampere current.

Claim 14

Dependent Claim 16 words

The transmitter of claim 8 wherein the control signal is representative of a desired linearity adjustment.

Claim 15

Dependent Claim 23 words

The transmitter of claim 9 and further including temperature response means coupled to the control means for temperature compensation of the span adjustment.

Claim 16

Dependent Claim 129 words

A transmitter for providing an analog output signal representative of a sensed parameter and representative of an input signal for controlling transmitter adjustment, comprising: 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.

Claim 17

Dependent Claim 129 words

A transmitter for providing an analog output signal representative of a sensed parameter and representative of an input signal for controlling transmitter adjustment, comprising: 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.

Claim 18

Dependent Claim 21 words

The transmitter of claim 15 and further comprising: integrator means coupled to the switching means for damping the analog output signal.

Claim 19

Dependent Claim 41 words

The transmitter of claim 16 wherein the transmitter means further comprises: feedback means coupled to the output means for providing a feedback signal representative of the analog output signal to the output means such that the analog output signal is stabilized.

Claim 20

Dependent Claim 14 words

The transmitter of claim 17 wherein the sensor means comprise a capacitive pressure sensor.

Claim 21

Dependent Claim 19 words

The transmitter of claim 17 wherein the digital means comprises a serial data input for receiving a transmitter adjustment.

Claim 22

Dependent Claim 19 words

The transmitter of claim 19 wherein the digital means further comprises a non-volatile memory for storing a transmitter adjustment.

Claim 23

Dependent Claim 117 words

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: 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; and analog 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.

Claim 24

Dependent Claim 117 words

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: 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; and analog 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.

Claim 25

Dependent Claim 54 words

The two wire transmitter of claim 21 wherein the converting means comprises: digital-to-analog (D/A) converter means for converting digital inputs to analog correction signals; and digital computer means coupled to the storage means and the D/A converter means for providing the digital inputs to the D/A converter means based upon the digital correction values.

Claim 26

Dependent Claim 29 words

The two wire transmitter of claim 22 wherein the D/A converter means produces pulse width modulated output signals having duty cycles which are a function of the digital inputs.

Claim 27

Dependent Claim 44 words

The two wire transmitter of claim 23 wherein the converting means further comprises: means coupled to the D/A converter means for converting the pulse width modulated output signals to the analog correction signals having magnitudes which are a function of the digital correction values.

Claim 28

Dependent Claim 29 words

The two wire transmitter of claim 24 wherein the means for converting the pulse width modulated output signals comprises integrator means for integrating the pulse width modulated output signals.

Claim 29

Dependent Claim 26 words

The two wire transmitter of claim 23 wherein the pulse width modulated output signals include span and zero signals for providing span and zero corrections, respectively.

Claim 30

Dependent Claim 60 words

The two wire transmitter of claim 26 and further comprising: means for providing an analog feedback signal which is a function of the loop current; and wherein the converting means further comprises: means for producing, as one of the analog correction signals, a span corrected feedback signal which is a function of the analog feedback signal and the span signal.

Claim 31

Dependent Claim 35 words

The two wire transmitter of claim 22 and further comprising: correction input means for providing input signals to the digital computer means to cause the digital computer means to change the digital correction values stored.

Claim 32

Dependent Claim 101 words

The two wire transmitter of claim 21 wherein the sensing means for producing an analog sensor signal comprises: variable reactance sensor means having a reactance which varies responsive to the parameter; drive means coupled to the variable reactance sensor means for providing a time varying drive signal to the variable reactance sensor means; means coupled to the variable reactance sensor means for deriving the analog sensor signal from the variable reactance sensor means; and drive control means coupled to the drive means for controlling the drive means to cause the analog sensor signal to have a predetermined relationship to the parameter.

Claim 33

Dependent Claim 43 words

The two wire transmitter of claim 29 wherein the analog correction signals include at least one linearization signal for correcting nonlinearity of the analog sensor signal with respect to the parameter, and wherein the drive control means is responsive to the linearization signal.

Claim 34

Dependent Claim 67 words

The two wire transmitter of claim 29 wherein the drive means comprises: clock means for providing a clock signal having a predetermined frequency; and means coupled to the clock means and the variable reactance sensor means for selectively providing clock pulses of the clock signal to the variable reactance sensor means as the drive signal as a function of a control signal from the drive control means.

Claim 35

Dependent Claim 105 words

The two wire transmitter of claim 31 wherein the converting means comprises: pulse width modulation digital-to-analog (D/A) converter means for producing pulse width modulated output signals having duty cycles which are a function of digital inputs, the D/A converter means having a clock input for receiving the clock signal; means coupled to the D/A converter means for converting the pulse width modulated output signals to the analog correction signals; and digital computer means coupled to the D/A converter means for providing the digital inputs as a function of the digital correction values, the digital computer means operating at a frequency determined by the clock signal.

Claim 36

Dependent Claim 34 words

The two wire transmitter of claim 28 wherein the correction input means comprises an analog-to-digital converter providing the input signals and a potentiometer coupled to the analog-to-digital converter for providing an analog signal thereto.

Claim 37

Dependent Claim 14 words

The two wire transmitter of claim 33 wherein the correction input means adjusts span.

Claim 38

Dependent Claim 21 words

The two wire transmitter of claim 28 wherein the correction input means comprises current sensing means for sensing the loop current.

Claim 39

Dependent Claim 100 words

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.

Claim 40

Dependent Claim 100 words

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.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-11-08	1992-05-09	1992-11-08	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-11-08	1996-05-09	1996-11-08	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-11-08	2000-05-09	2000-11-08	$7700.00	Window Closed / Lapsed

Analog transducer circuit with digital control

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