Patent US3796993A successfully refreshed from Google Patents.
US3796993A
Expired / Lapsed
US
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Analog input device for data transmission systems
Assignee: American Multiplex Systems Inc
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Filing: 1971-10-04
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Granted: 1974-03-12
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Expires: 1991-10-04
Abstract
Abstract An analog input device for data transmission systems wherein a digital address message from a central station to a plurality of remote terminals initiates sequential scanning of the analog parameter points at the addressed remote terminal. A sensor has a resistance which varies in accordance with the magnitude of its associated analog parameter point, and a time-shared differential sensing circuit measures the voltage drop across the variable resistance of the sensor while a pulse of a precise reference current passes from a time-shared trunk line through the sensor.
Inventors
- 👤 H Lewis
- 👤 D Fox
- 👤 R Ichinose
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 19:01
CPC Classifications
G; G08; G08C; G08C15/00; G08C15/06
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
190 words
A method of obtaining analog input signals from a plurality of independent sensors each displaced an appreciable distance from each other and each having a resistance which varies according to the magnitude of its own associated analog parameter point including the steps of: generating a precision direct current; and monitoring repeatedly the resistance value of each sensor over a substantial period of time to detect any variation of the magnitude of its associated parameter, said monitoring step including conducting a pulse of said precision current through said sensor during a first time period while simultaneously measuring the voltage differential between the beginning and end points of the sensor, and terminating and ceasing said conduction and measuring steps during a second time period subsequent to and substantially longer than said first time period to prevent the magnitude of the resistance from increasing due to self heating caused by the current passing through the sensor, and wherein said conducting and measuring steps are sequentially performed on each of the other sensors during the second time period without performing said conducting and measuring steps on more than one sensor at any given time.
Claim 2
Independent Claim
190 words
A method of obtaining analog input signals from a plurality of independent sensors each displaced an appreciable distance from each other and each having a resistance which varies according to the magnitude of its own associated analog parameter point including the steps of: generating a precision direct current; and monitoring repeatedly the resistance value of each sensor over a substantial period of time to detect any variation of the magnitude of its associated parameter, said monitoring step including conducting a pulse of said precision current through said sensor during a first time period while simultaneously measuring the voltage differential between the beginning and end points of the sensor, and terminating and ceasing said conduction and measuring steps during a second time period subsequent to and substantially longer than said first time period to prevent the magnitude of the resistance from increasing due to self heating caused by the current passing through the sensor, and wherein said conducting and measuring steps are sequentially performed on each of the other sensors during the second time period without performing said conducting and measuring steps on more than one sensor at any given time.
Claim 3
Dependent Claim
32 words
The method of claim 1 wherein said monitoring step is performed on a plurality of separate temperature sensors each having a resistance which varies in direct proportion to its change of temperature.
Claim 4
Independent Claim
117 words
A method of obtaining analog input signals from a plurality of sensors each having a resistance which varies according to the magnitude of an associated analog parameter point including the steps of: generating a precision current including applying a supply voltage to a pair of matched transistors having a common base voltage to produce two identical current outputs, monitoring one of the current outputs to detect any variation in current output, and changing the base voltage to compensate for and eliminate any variation in current output detected by said monitoring step; conducting a pulse of the precision current through a sensor; and measuring the voltage drop across the variable resistance of said sensor during said conducting step.
Claim 5
Independent Claim
117 words
A method of obtaining analog input signals from a plurality of sensors each having a resistance which varies according to the magnitude of an associated analog parameter point including the steps of: generating a precision current including applying a supply voltage to a pair of matched transistors having a common base voltage to produce two identical current outputs, monitoring one of the current outputs to detect any variation in current output, and changing the base voltage to compensate for and eliminate any variation in current output detected by said monitoring step; conducting a pulse of the precision current through a sensor; and measuring the voltage drop across the variable resistance of said sensor during said conducting step.
Claim 6
Dependent Claim
110 words
The method of claim 1 wherein said conducting step includes conducting a pulse of the precision direct current to and from each sensor through its own two-wire transmission line; said measuring step includes measuring the voltage drop across the variable resistance of each sensor through its own two-wire monitoring line separate from said two wire transmission lines and connected thereto only at the opposite ends respectively of such sensor; and said monitoring step further including time-sharing a single trunk line to carry the precision current sequentially to the two-wire transmission line of each sensor, and time-sharing a single differential amplifier circuit connected to the two-wire monitoring line of each sensor.
Claim 7
Dependent Claim
301 words
Apparatus for obtaining analog input signals from a plurality of independent sensors displaced apart from each other and each having a resistance which varies according to the magnitude of its own associated analog parameter point, including: current source means for generating a precision direct current; a trunk line connected to said current source means; a plurality of separate current transmission lines each connected in series with a sensor and in parallel through its own respective current switch to said trunk line to carry a pulse of direct current through a particular sensor only when said current switch is closed; differential amplifier means for measuring the voltage drop across each of said sensors; a separate pair of detection lines for each sensor connected at one end through their own respective pair of detection switches to said differential amplifier means, and connected at the other end to said current transmission line immediately adjacent the ends of the sensor to measure only the voltage drop across the sensor itself while said pulse of direct current is passing therethrough; shield means surrounding the transmission and detection lines for each sensor to prevent errors caused by extraneous voltages; switching means connected to all of said transmission and detection switches for repeatedly monitoring the resistance value of each sensor over a substantial period of time by sequentially operating said switches to simultaneously connect said generating means and said differential amplifier means to only a single sensor at a time to allow a pulse of said precision current to pass through said sensor during a first short time interval while said differential amplifier means measures the voltage drop across the variable resistance of said sensor, and for disconnecting said sensor during a subsequent longer second time interval to prevent self-heating of the sensor due to current flow therethrough.
Claim 8
Dependent Claim
301 words
Apparatus for obtaining analog input signals from a plurality of independent sensors displaced apart from each other and each having a resistance which varies according to the magnitude of its own associated analog parameter point, including: current source means for generating a precision direct current; a trunk line connected to said current source means; a plurality of separate current transmission lines each connected in series with a sensor and in parallel through its own respective current switch to said trunk line to carry a pulse of direct current through a particular sensor only when said current switch is closed; differential amplifier means for measuring the voltage drop across each of said sensors; a separate pair of detection lines for each sensor connected at one end through their own respective pair of detection switches to said differential amplifier means, and connected at the other end to said current transmission line immediately adjacent the ends of the sensor to measure only the voltage drop across the sensor itself while said pulse of direct current is passing therethrough; shield means surrounding the transmission and detection lines for each sensor to prevent errors caused by extraneous voltages; switching means connected to all of said transmission and detection switches for repeatedly monitoring the resistance value of each sensor over a substantial period of time by sequentially operating said switches to simultaneously connect said generating means and said differential amplifier means to only a single sensor at a time to allow a pulse of said precision current to pass through said sensor during a first short time interval while said differential amplifier means measures the voltage drop across the variable resistance of said sensor, and for disconnecting said sensor during a subsequent longer second time interval to prevent self-heating of the sensor due to current flow therethrough.
Claim 9
Dependent Claim
207 words
Apparatus for obtaining analog input signals from a plurality of sensors each having a resistance which varies according to the magnitude of an associated analog parameter point, indluding: means for generating a precision current including a pair of matched transistors having a common base, monitoring circuit means connected to one of said transistors for detecting variations in the magnitude of precision current being generated, and feed-back circuit means coupling said monitoring circuit means to said common base of said matched transistors for eliminating any detected variations of said precision current; separate transmission circuit means associated with each of said sensors, respectively, for connecting said generating means with each of said sensors; differential amplifier means for measuring the voltage drop across said sensors; separate detection circuit means associated with each of said sensors, respectively, for connecting said differential amplifier means with each of said sensors; and switching means coupled to each of said transmission and detection circuit means for simultaneously connecting said generating means and said differential amplifier means to only a single sensor to allow a pulse of said precision current to pass through said sensor during a short time interval while said differential amplifier means measures the voltage drop across the variable resistance of said sensor.
Claim 10
Dependent Claim
207 words
Apparatus for obtaining analog input signals from a plurality of sensors each having a resistance which varies according to the magnitude of an associated analog parameter point, indluding: means for generating a precision current including a pair of matched transistors having a common base, monitoring circuit means connected to one of said transistors for detecting variations in the magnitude of precision current being generated, and feed-back circuit means coupling said monitoring circuit means to said common base of said matched transistors for eliminating any detected variations of said precision current; separate transmission circuit means associated with each of said sensors, respectively, for connecting said generating means with each of said sensors; differential amplifier means for measuring the voltage drop across said sensors; separate detection circuit means associated with each of said sensors, respectively, for connecting said differential amplifier means with each of said sensors; and switching means coupled to each of said transmission and detection circuit means for simultaneously connecting said generating means and said differential amplifier means to only a single sensor to allow a pulse of said precision current to pass through said sensor during a short time interval while said differential amplifier means measures the voltage drop across the variable resistance of said sensor.
Claim 11
Dependent Claim
218 words
A data transmission system for transmitting binary address messages from a central station to a plurality of remote terminals each having a single low-voltage power supply, and for transmitting binary response messages from the addressed remote terminal to the central station, wherein one of said remote terminals includes: a plurality of sensors each having a resistance which varies according to the magnitude of an associated analog parameter point; first circuit means connected in parallel with each of said plurality of sensors for carrying a current through said sensors; a precision current supply circuit connected to said first circuit means; second circuit means connected in parallel with each of said plurality of sensors and aligned with and adjacent to said first circuit means for measuring the variable resistance of said sensors while said precision current is passing therethrough; a shield member surrounding the aligNed portions of said first and second circuit means; switching means connected with said first and second circuit means for allowing a pulse of said precision current to pass through only one sensor at a time while limiting the measurement of said voltage drop to said particular sensor carrying said precision current pulse; and wherein said single low-voltage power supply is connected to said precision current supply circuit, said second circuit means and said switching means.
Claim 12
Dependent Claim
218 words
A data transmission system for transmitting binary address messages from a central station to a plurality of remote terminals each having a single low-voltage power supply, and for transmitting binary response messages from the addressed remote terminal to the central station, wherein one of said remote terminals includes: a plurality of sensors each having a resistance which varies according to the magnitude of an associated analog parameter point; first circuit means connected in parallel with each of said plurality of sensors for carrying a current through said sensors; a precision current supply circuit connected to said first circuit means; second circuit means connected in parallel with each of said plurality of sensors and aligned with and adjacent to said first circuit means for measuring the variable resistance of said sensors while said precision current is passing therethrough; a shield member surrounding the aligNed portions of said first and second circuit means; switching means connected with said first and second circuit means for allowing a pulse of said precision current to pass through only one sensor at a time while limiting the measurement of said voltage drop to said particular sensor carrying said precision current pulse; and wherein said single low-voltage power supply is connected to said precision current supply circuit, said second circuit means and said switching means.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-11 | 1977-09-10 | 1978-03-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-11 | 1981-09-10 | 1982-03-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-11 | 1985-09-10 | 1986-03-12 | $7700.00 | Window Closed / Lapsed |