Multiple remote sensor system for real time analog sensing and differential cummunication
First Claim
1. A communication system comprisinga host station;
- a plurality of remote stations each associated with a sensor;
a first wire and a second wire forming a first pair of lines to which the plurality of remote stations are coupled in shunt, and which the host station can use to address any one of the plurality of remote stations with which it desires to communicate and can use to substantially continuously supply power to the remote stations;
a source of power having a positive terminal and a negative terminal;
first switch means controlled by the host, and connected to the positive terminal of the source of power and to the first pair of lines for connecting the positive terminal to the first wire when a first signal state is issued by the host, and for connecting the positive terminal to the second wire when a second signal state is issued by the host;
second switch means controlled by the host and connected to the negative terminal of the source of power and to the first pair of lines for connecting the negative terminal to the second wire when the first signal state is issued by the host and for connecting the negative terminal to the first wire when the second signal state is issued by the host, so that the host can place differential address and control signals upon the first pair of lines while power is being supplied to the remote stations on the first pair of lines;
a second pair of lines, separate from the first pair of lines, which the host station can use to receive differential signals communicated to it by an addressed remote station; and
wherein each of the remote stations operates with voltages and currents compatible with hazardous area requirements and includesreceiving means coupled to the first pair of lines and responsive to the differential address and control signals from the host station for determining when the host station is addressing the remote station and thereupon issuing a transmitter enable signal, and for extracting control information from the differential address and control signals;
means for receiving a sensor signal;
transmitting means which are normally in a quiescent state and responsive to the extracted control information for transmitting a real time differential voltage signal to the host station over the second pair of lines when the transmitter enable signal is issued by the receiving means, wherein the real time differential voltage signal is selected by the extracted control information from among the sensor signal, a first analog signal having a magnitude which is the full scale value of the sensor signal, and a second analog signal having a magnitude which is the zero level for the sensor signal, and wherein the transmitting means maintains the sensor in a quiescent state until the transmitter enable signal is issued, and further wherein the transmitting means are configured so that, when the sensor signal is selected for transmission, the real time differential voltage signal which is transmitted changes in real time in proportion to real time changes in the sensor signal, and the rate of change of the real time differential voltage signal is in real time and in proportion to the rate of change of the sensor signal, so that the differential voltage signal retains substantially all of the dynamic character of the sensor signal, and the information content of the sensor signal is substantially preserved in the differential voltage signal, and further wherein the sensor signal can have frequencies on the order of several thousand hertz.
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Accused Products
Abstract
A four-wire system is disclosed for communicating between the host station and several remote stations. A first pair of wires is employed across which the remote stations are coupled in shunt, and over which the host station addresses the particular remote station with which it wishes to communicate, and supplies power to the several remote stations. The remote stations are coupled in shunt to a second pair of wires and transmit real time analog information to the host station over the second pair of wires. Each remote station includes a receiving section, which determines whether an address appearing on the first pair of wires corresponds to the particular remote station, and if so, activates power to a transmitting section therein. The transmitting section responds to control information extracted by the receiving section from the address and transmits selected real time information back to the host station over the second pair of wires by way of a differential voltage format. The control information includes instructions as to the source of real time information to be transmitted by the transmitting section to the host station.
67 Citations
18 Claims
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1. A communication system comprising
a host station; -
a plurality of remote stations each associated with a sensor; a first wire and a second wire forming a first pair of lines to which the plurality of remote stations are coupled in shunt, and which the host station can use to address any one of the plurality of remote stations with which it desires to communicate and can use to substantially continuously supply power to the remote stations; a source of power having a positive terminal and a negative terminal; first switch means controlled by the host, and connected to the positive terminal of the source of power and to the first pair of lines for connecting the positive terminal to the first wire when a first signal state is issued by the host, and for connecting the positive terminal to the second wire when a second signal state is issued by the host; second switch means controlled by the host and connected to the negative terminal of the source of power and to the first pair of lines for connecting the negative terminal to the second wire when the first signal state is issued by the host and for connecting the negative terminal to the first wire when the second signal state is issued by the host, so that the host can place differential address and control signals upon the first pair of lines while power is being supplied to the remote stations on the first pair of lines; a second pair of lines, separate from the first pair of lines, which the host station can use to receive differential signals communicated to it by an addressed remote station; and wherein each of the remote stations operates with voltages and currents compatible with hazardous area requirements and includes receiving means coupled to the first pair of lines and responsive to the differential address and control signals from the host station for determining when the host station is addressing the remote station and thereupon issuing a transmitter enable signal, and for extracting control information from the differential address and control signals; means for receiving a sensor signal; transmitting means which are normally in a quiescent state and responsive to the extracted control information for transmitting a real time differential voltage signal to the host station over the second pair of lines when the transmitter enable signal is issued by the receiving means, wherein the real time differential voltage signal is selected by the extracted control information from among the sensor signal, a first analog signal having a magnitude which is the full scale value of the sensor signal, and a second analog signal having a magnitude which is the zero level for the sensor signal, and wherein the transmitting means maintains the sensor in a quiescent state until the transmitter enable signal is issued, and further wherein the transmitting means are configured so that, when the sensor signal is selected for transmission, the real time differential voltage signal which is transmitted changes in real time in proportion to real time changes in the sensor signal, and the rate of change of the real time differential voltage signal is in real time and in proportion to the rate of change of the sensor signal, so that the differential voltage signal retains substantially all of the dynamic character of the sensor signal, and the information content of the sensor signal is substantially preserved in the differential voltage signal, and further wherein the sensor signal can have frequencies on the order of several thousand hertz. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A communication system comprising
a host station; -
a plurality of remote stations, each of which can be associated with a different sensor means; a first pair of lines to which the remote stations are coupled in shunt, and which is used by the host station to substantially continuously supply power to the remote stations ad to uniquely select and control any of the remote stations by way of differential address and control signals; a second pair of lines, separate from the first pair, to which the remote stations are coupled in shunt, and which the host station can use to receive differential voltage signals communicated to it by one or more selected remote stations; and wherein each of the remote stations operates at voltages and currents compatible with hazardous area requirements and includes means responsive to address and control signals received on the first pair of lines from the host station for differentially transmitting information to the host over the second pair of lines when the remote station is addressed by the host, wherein the information transmitted is designated by the received control signals and can include a full scale voltage and a zero scale voltage for signal calibration, sensor condition information, and real time dynamic signals from a transducer, and wherein transmission of the designated information continues until control signals are received by the remote station to cease transmission, and further wherein the means for differentially transmitting information includes driving means which are configured so that when the real time dynamic signals from the transducer are transmitted, the differentially transmitted information changes in real time in proportion to the real time changes in the transducer signal and the rate of change of the differentially transmitted information is in real time and in proportion to the rate of change of the transducer signal, so that the differentially transmitted information retains substantially all of the dynamic character of the transducer signal and the information content of the transducer signal is substantially preserved, and further wherein the transducer signal can have frequencies on the order of several thousand hertz. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for communication between a host station and a plurality of remote stations
(1) connecting each of the plurality of remote stations in shunt across a first pair of lines; -
(2) supplying power to the remote stations by way of the first pair of lines; (3) communicating information from the remote stations to the host station by way of a second pair of lines different from the first pair of lines; (4) coupling the host station to the first pair of lines by way of switching means controllable by the host station; (5) connecting a source of power in series with the switching means and the lines in the first pair of lines to substantially continuously supply power to the plurality of remote stations; (6) alternating the polarity of the connection of the source of power to the pair of lines by controlling the switching means in response to bit serial addresses from the host station to address particular ones of the plurality of remote stations; and (7) causing the particular addressed remote station to place a differential voltage signal on the second pair of lines which is in the form of real time signal from the addressed remote station and which is selected from a full scale voltage and a zero scale voltage for signal calibration, sensor condition information, and real time dynamic signals from a transducer, and further employing driving means which are configured so that when the real time dynamic signal from the transducer are placed on the second pair of lines, the real time dynamic signal changes in real time in proportion to the real time changes in the transducer signal and the rate of change of the real time dynamic signal is in real time and in proportion to the rate of change of the transducer signal, so that the real time dynamic signal retains substantially all of the dynamic character of the transducer signal and the information content of the transducer signal is substantially preserved in the real time dynamic signal, and further wherein the transducer signal can have frequencies on the order of several thousand hertz. - View Dependent Claims (17)
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18. A communication system comprising:
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a host station; a plurality of remote stations, each of which can be associated with a different transducer which provides a transducer signal; a first wire and a second wire forming a first pair of lines to which the remote stations are connected in shunt, and which carry operating power from the host station to the remote stations, and further which carry differential address and control signals from the host station to the remote stations; a source of operating power located at the host station and having a positive terminal and a negative terminal; switch means controlled by signals issued by the host station for connecting the positive terminal of the source of operating power to the first wire of the first pair of lines and the negative terminal to the second wire of the first pair of lines when the signals issued by the host station have a first logic state, and for connecting the positive terminal to the second wire and the negative terminal to the first wire when the signals issued by the host station have a second logic state, so that the host station can place on the first pair of lines differential address and control signals for the remote stations while substantially continuously supplying operating power to the remote stations; a second pair of lines, different from the first pair, to which the remote stations are coupled in shunt, and which carries real time, analog signals in differential form from the remote stations to the host station, wherein each of the remote stations comprise means coupled to the first pair of lines for extracting address and control information from the differential address and control signals, for continuously extracting operating power at an operating voltage referenced to a signal-common potential from the first pair of lines, and for issuing a transmitter enable signal when the address and control information indicate that the remote station is to communicate with the host station; and transmitter means which are normally in a quiescent state and which are coupled to the extracting means, to the transducer means, and to the second pair of lines, for transmitting real time, analog signals in differential form on the second pair of lines when the transmitter enable signal is issued, the transmitter means including means for differentially driving the second pair of lines with a differential voltage form of either the transducer signal, the operating voltage, or the signal-common potential as selected by the extracted control information, wherein the driving means are configured so that the differential voltage form of the transducer signal changes in real time in proportion to the real time changes in the transducer signal and the rate of change of the differential voltage form of the transducer signal is in real time and in proportion to the rate of change of the transducer signal so that the differential voltage form retains substantially all of the dynamic character of the actual transducer signal and the information content of the transducer signal is substantially preserved in the differential voltage form, and further wherein the actual transducer signal can have frequencies on the order of several thousand hertz.
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Specification