US4475103A
Expired / Lapsed
US
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Integrated-circuit thermocouple signal conditioner
Assignee: Analog Devices Inc
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Filing: 1982-02-26
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Granted: 1984-10-02
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Expires: 2002-02-26
Abstract
Abstract An integrated-circuit thermocouple signal conditioner having on a single chip an amplifier and a transistor circuit responsive to the chip temperature for developing a cold-junction compensation signal referred to 0° Celsius. The amplifier includes two matched differential input amplifiers the outputs of which are summed and used to control a high-gain main amplifier. Thermocouple signals are applied to one of the input amplifiers, serving as a floating input stage, and the main amplifier output is connected through a feedback network to the input of the other differential amplifier. A cold junction compensation signal also is applied to the input of the other differential amplifier. The compensation is a differential voltage proportional to the Celsius temperature of the chip; the compensation voltage comprises two components having positive and negative temperature coefficients. The IC chip also includes alarm transistors for indicating overload conditions resulting from open-circuited thermocouple leads or other overloads.
Inventors
- 👤 Adrian P. Brokaw
- 👤 Barrie Gilbert
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:11
CPC Classifications
G; G01; G01K; G01K7/00; G01K7/02; G01K7/10; G01K7/12; G01K7/13
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
142 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means having differential input means; thermocouple input terminal means connected to said input means and providing a reference junction at the chip temperature when connected to thermocouple leads; temperature-responsive signal source means formed as part of said chip and coupled to said input means additively with respect to the thermocouple signal, the signal produced by said signal source means effecting reference junction compensation corresponding to changes in the chip temperature; and a negative feedback circuit connected between the output of said amplifier means and said input means; the feedback of said feedback circuit forcing the output of said amplifier to vary in correspondence to changes in the thermocouple voltage resulting from changes in the measurement temperature.
Claim 2
Dependent Claim
142 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means having differential input means; thermocouple input terminal means connected to said input means and providing a reference junction at the chip temperature when connected to thermocouple leads; temperature-responsive signal source means formed as part of said chip and coupled to said input means additively with respect to the thermocouple signal, the signal produced by said signal source means effecting reference junction compensation corresponding to changes in the chip temperature; and a negative feedback circuit connected between the output of said amplifier means and said input means; the feedback of said feedback circuit forcing the output of said amplifier to vary in correspondence to changes in the thermocouple voltage resulting from changes in the measurement temperature.
Claim 3
Dependent Claim
16 words
An IC chip according to claim 1 wherein said signal source means comprises a PTAT source.
Claim 4
Dependent Claim
62 words
An IC chip according to claim 1, including a CTAT signal source connected to said amplifier input means to apply thereto a voltage to effect zero suppression of the reference junction compensation; said reference junction compensation providing a voltage simulating the thermocouple output voltage when the thermocouple measurement junction is at the chip temperature and the reference junction is at 0° Celsius.
Claim 5
Dependent Claim
25 words
An IC chip according to claim 3, wherein said CTAT signal source is arranged to produce a net compensation signal referenced to zero degrees Celsius.
Claim 6
Dependent Claim
34 words
An IC chip according to claim 1, wherein said signal source means comprises a PTAT signal source and a CTAT signal source arranged to produce a net compensation signal referenced to zero degrees Celsius.
Claim 7
Dependent Claim
50 words
An IC chip according to claim 1, wherein said amplifier means comprises first and second matched differential amplifiers with their outputs connected together in summation; said thermocouple input terminal means being connected to said first differential amplifier; said feedback circuit being connected to the input of said second differential amplifier.
Claim 8
Dependent Claim
23 words
An IC chip according to claim 6, wherein said temperature-responsive signal source means is connected to the input of said second differential amplifier.
Claim 9
Dependent Claim
23 words
An IC chip according to claim 7, wherein said temperature-responsive signal source means comprises a PTAT signal source and a CTAT signal source.
Claim 10
Dependent Claim
43 words
An IC chip according to claim 8, wherein said second differential amplifier includes first and second input terminals; said PTAT signal source being connected to one of said input terminals; said CTAT signal source being connected to the other of said input terminals.
Claim 11
Dependent Claim
46 words
An IC chip according to claim 1, wherein said temperature-responsive signal source means comprises a set of interconnected transistors at least one of which has a substantially different current density than another of said transistors, thereby to produce a PTAT voltage for compensating the reference junction.
Claim 12
Dependent Claim
39 words
An IC chip according to claim 1, wherein said temperature-responsive signal source means comprises a transistor carrying a PTAT current so as to develop between the base and emitter thereof a CTAT voltage for compensating the thermocouple reference junction.
Claim 13
Dependent Claim
129 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means having input means and output means, said output means producing an output measurement signal which varies in correspondence to changes in the temperature measurement signal; thermocouple input terminal means connected to said input means; temperature-responsive signal source means forming part of said chip and coupled to said input means to effect reference junction compensation corresponding to changes in the chip temperature; an alarm transistor; and alarm circuit means coupled to said amplifier means and responsive to variations in the temperature measurement signal, said alarm circuit means including means for actuating said alarm transistor in the event that a thermocouple lead becomes open-circuited.
Claim 14
Dependent Claim
129 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means having input means and output means, said output means producing an output measurement signal which varies in correspondence to changes in the temperature measurement signal; thermocouple input terminal means connected to said input means; temperature-responsive signal source means forming part of said chip and coupled to said input means to effect reference junction compensation corresponding to changes in the chip temperature; an alarm transistor; and alarm circuit means coupled to said amplifier means and responsive to variations in the temperature measurement signal, said alarm circuit means including means for actuating said alarm transistor in the event that a thermocouple lead becomes open-circuited.
Claim 15
Dependent Claim
34 words
An IC chip according to claim 12, wherein said alarm circuit means includes means operable to activate said alarm transistor in the event there is an overload on the output of the amplifier means.
Claim 16
Dependent Claim
21 words
An IC chip according to claim 12, including current-limiting means coupled to said alarm transistor to prevent excessive current flow therethrough.
Claim 17
Dependent Claim
142 words
An IC chip including a thermocouple amplifier with reference junction compensation comprising: a first differential amplifier having an input circuit arranged to receive the thermocouple signal; a pair of thermocouple input terminals connected to said input circuit; a second differential amplifier matched to said first amplifier; a main amplifier combining the outputs of said two amplifiers to produce an output signal corresponding to the difference between said outputs; a negative feedback circuit connecting the output of said combining means to the input of said second differential amplifier; and signal source means forming part of said IC chip and coupled to the input of said second differential amplifier to effect reference junction compensation; said input circuit of said first differential amplifier being isolated from any feedback, to assure that the thermocouple leads are presented with an amplifier input impedance unaffected by feedback circuitry.
Claim 18
Dependent Claim
142 words
An IC chip including a thermocouple amplifier with reference junction compensation comprising: a first differential amplifier having an input circuit arranged to receive the thermocouple signal; a pair of thermocouple input terminals connected to said input circuit; a second differential amplifier matched to said first amplifier; a main amplifier combining the outputs of said two amplifiers to produce an output signal corresponding to the difference between said outputs; a negative feedback circuit connecting the output of said combining means to the input of said second differential amplifier; and signal source means forming part of said IC chip and coupled to the input of said second differential amplifier to effect reference junction compensation; said input circuit of said first differential amplifier being isolated from any feedback, to assure that the thermocouple leads are presented with an amplifier input impedance unaffected by feedback circuitry.
Claim 19
Dependent Claim
15 words
Apparatus as claimed in claim 15, wherein said signal source means comprises a PTAT source.
Claim 20
Dependent Claim
32 words
Apparatus as claimed in claim 16, wherein said signal source means comprises means to zero suppress the compensation signal developed by said PTAT source to provide a reference point at 0° Celsius.
Claim 21
Dependent Claim
16 words
Apparatus as claimed in claim 17, wherein said zero suppression means comprises a CTAT signal source.
Claim 22
Dependent Claim
81 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means having input means and output means; thermocouple input terminal means connected to said input means; temperature-responsive signal source means coupled to said input means to effect reference junction compensation corresponding to changes in the chip temperature; said temperature-responsive signal source means producing a compensation signal corresponding to a reference temperature of zero degrees Celsius.
Claim 23
Dependent Claim
81 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means having input means and output means; thermocouple input terminal means connected to said input means; temperature-responsive signal source means coupled to said input means to effect reference junction compensation corresponding to changes in the chip temperature; said temperature-responsive signal source means producing a compensation signal corresponding to a reference temperature of zero degrees Celsius.
Claim 24
Dependent Claim
38 words
An IC chip according to claim 19, wherein said signal source means comprises a PTAT source and a second signal source arranged to zero-suppress the compensation signal to produce a composite compensation signal corresponding to zero degrees Celsius.
Claim 25
Dependent Claim
17 words
An IC chip according to claim 20, wherein said second signal source includes a CTAT signal source.
Claim 26
Dependent Claim
168 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means having input means and output means; thermocouple input terminal means connected to said input means and presenting an impedance to thermocouple leads connected to said input terminal means; said input means being isolated from all other portions of said amplifier means to assure that the impedance presented to thermocouple leads connected to said input terminal means will be unaffected by connections from said input means to such other portions; transistor means; circuit means connected to said transistor means to produce therefrom a signal responsive to the temperature of the chip and serving as a reference junction compensation signal which changes in correspondence with changes in the chip temperature; said circuit means including means connecting said reference junction compensation signal to said amplifier to act together with the thermocouple signal at said input means to determine the output of said amplifier means.
Claim 27
Dependent Claim
168 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means having input means and output means; thermocouple input terminal means connected to said input means and presenting an impedance to thermocouple leads connected to said input terminal means; said input means being isolated from all other portions of said amplifier means to assure that the impedance presented to thermocouple leads connected to said input terminal means will be unaffected by connections from said input means to such other portions; transistor means; circuit means connected to said transistor means to produce therefrom a signal responsive to the temperature of the chip and serving as a reference junction compensation signal which changes in correspondence with changes in the chip temperature; said circuit means including means connecting said reference junction compensation signal to said amplifier to act together with the thermocouple signal at said input means to determine the output of said amplifier means.
Claim 28
Dependent Claim
23 words
An IC chip according to claim 22, wherein said transistor means includes means to produce a zero-suppression signal responsive to the chip temperature.
Claim 29
Dependent Claim
124 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means with input and output means; said amplifier means having a PTAT offset voltage; thermocouple input terminal means connected to said input means; PTAT signal source means coupled to said input means to effect reference junction compensation corresponding to changes in the chip temperature; the output of said PTAT signal source means being adjustable in magnitude to provide for zeroizing of the amplifier with the PTAT offset voltages effectively combined with the output of said PTAT signal source means to substantially minimize error effects due to changes in the offset voltages with changes in temperature of the chip.
Claim 30
Dependent Claim
124 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means with input and output means; said amplifier means having a PTAT offset voltage; thermocouple input terminal means connected to said input means; PTAT signal source means coupled to said input means to effect reference junction compensation corresponding to changes in the chip temperature; the output of said PTAT signal source means being adjustable in magnitude to provide for zeroizing of the amplifier with the PTAT offset voltages effectively combined with the output of said PTAT signal source means to substantially minimize error effects due to changes in the offset voltages with changes in temperature of the chip.
Claim 31
Dependent Claim
18 words
An IC chip according to claim 24, including means to supply PTAT bias currents to said amplifier means.
Claim 32
Dependent Claim
102 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means with input means and output means; thermocouple input terminal means connected to said input means; temperature-responsive signal source means coupled to said input means to effect reference junction compensation corresponding to changes in the chip temperature; positive and negative supply rails for said amplifier means; and circuit means forming part of said amplifier means for controlling the output of said amplifier at thermocouple voltages which range down to the voltage of said negative supply rail.
Claim 33
Dependent Claim
102 words
An IC chip to which a thermocouple may be connected to produce a temperature measurement signal with reference junction compensation, said chip having formed thereon: amplifier means with input means and output means; thermocouple input terminal means connected to said input means; temperature-responsive signal source means coupled to said input means to effect reference junction compensation corresponding to changes in the chip temperature; positive and negative supply rails for said amplifier means; and circuit means forming part of said amplifier means for controlling the output of said amplifier at thermocouple voltages which range down to the voltage of said negative supply rail.
Claim 34
Dependent Claim
43 words
An IC chip according to claim 26, wherein said amplifier input means comprises a balanced pair of PNP transistors the bases of which are connected to said thermocouple input terminal means; the collectors of said transistors being connected to said negative supply rail.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-10-02 | 1988-04-02 | 1988-10-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-10-02 | 1992-04-02 | 1992-10-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-02 | 1996-04-02 | 1996-10-02 | $7700.00 | Window Closed / Lapsed |