Frequency feedback on a current loop of a current-to-pressure converter
First Claim
1. A current-to-pressure converter for providing an output pressure as a function of magnitude of a variable input DC current, the converter comprising:
- means for connecting the converter to a circuit through which the input DC current flows;
means for providing a feedback signal representative of the output pressure;
means for providing a control signal as a function of the magnitude of the input DC current and the feedback signal;
means for providing the output pressure as a function of the control signal; and
means for transmitting, over the circuit through which the input DC current flows, a time varying signal having a characteristic which indicates whether the converter is functioning properly.
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Accused Products
Abstract
A current-to-pressure (I/P) converter provides an output pressure as a function of the magnitude of a variable input DC current. The I/P converter includes a pressure sensor which produces a feedback signal representative of the output pressure. Based upon the feedback signal and the magnitude of the input DC current, an electrical control signal is produced which controls a device for varying the output pressure. The I/P converter also includes a circuit for generating a time-varying signal which is sent back over the current loop wires through which the input DC current flows. The time-varying signal provides an indication of whether the I/P converter is functioning properly. This permits diagnosis of possible causes of control system malfunctions without having to inspect the I/P converter itself.
46 Citations
12 Claims
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1. A current-to-pressure converter for providing an output pressure as a function of magnitude of a variable input DC current, the converter comprising:
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means for connecting the converter to a circuit through which the input DC current flows; means for providing a feedback signal representative of the output pressure; means for providing a control signal as a function of the magnitude of the input DC current and the feedback signal; means for providing the output pressure as a function of the control signal; and means for transmitting, over the circuit through which the input DC current flows, a time varying signal having a characteristic which indicates whether the converter is functioning properly. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An electrical control apparatus for providing an output fluid pressure at an output which is a function of a magnitude of a variable input DC current, the apparatus comprising:
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first and second terminals adapted to be connected in a circuit through which the variable input DC current flows, and wherein the control apparatus is energized solely by the variable input DC current flowing between the first and second terminals; first and second conductors connected to the first and second terminals, respectively; first circuit means for receiving the input DC current and providing an electrical signal representative of the magnitude of the input DC current; pressure sensor means for receiving the output pressure and providing an electrical signal representative of the output pressure; amplifier means for receiving the electrical signal representative of the magnitude of the input DC current and for receiving the electrical signal representative of the output pressure and providing a control signal which is a function thereof; output transducing means for providing the output pressure controlled by the control signal; circuit means for receiving the electrical signal representative of the output pressure and providing a signal having a frequency representative of the output pressure; and interface means for receiving the signal having a frequency representative of the output pressure and non-interferingly superimposing a time varying signal having the frequency representative of the output pressure on the input DC current.
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Specification