Patent US4573431A successfully refreshed from Google Patents.
Patent US3842349A successfully refreshed from Google Patents.
US3842349A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic ac/dc rms comparator
Assignee: National Research Council Canada
•
Filing: 1973-08-07
•
Granted: 1974-10-15
•
Expires: 1993-08-07
Abstract
Abstract This invention is directed to an improved apparatus for the accurate comparison of an ac voltage with an accurate dc voltage standard to obtain the RMS value of the ac voltage. The voltages are alternately applied to the first heater of a differential multijunction thermal converter. The voltage generated by the converter is applied to a feedback circuit which includes a series connected amplifier, integrator and inverter and wherein the sum of the amplifier and inverter outputs is applied to the second heater in the converter. A pair of sample-and-hold circuits are alternately connected to the inverter output such that they obtain dc voltages representative of the ac and dc voltages respectively. The difference between the representative dc voltages is applied to a zero-centre meter or recorder.
Inventors
- 👤 L Cox
- 👤 N Kusters
- 👤 M Macmartin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:41
CPC Classifications
G; G01; G01R; G01R19/00; G01R19/04; G01R5/00; G01R5/22
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
128 words
An apparatus for comparing a first voltage to a second voltage comprising: a differential thermal converter means having a first and a second heater; first switch means for alternately connecting the first voltage and the second voltage to the first heater; first amplifier means coupled to the thermal converter; integrator-inverter means coupled to the first amplifier means; means for summing the outputs of the amplifier means and the Integrator-inverter means; means for coupling the summing means to the second heater; first and second sample-and-hold means; second switch means for alternately connecting the first and second sample-and-hold means to the integrator-inverter means output in synchronism with said first switch means; and means coupled to the first and second sample-and-hold means for providing the difference between the two sample-and-hold outputs.
Claim 2
Independent Claim
128 words
An apparatus for comparing a first voltage to a second voltage comprising: a differential thermal converter means having a first and a second heater; first switch means for alternately connecting the first voltage and the second voltage to the first heater; first amplifier means coupled to the thermal converter; integrator-inverter means coupled to the first amplifier means; means for summing the outputs of the amplifier means and the Integrator-inverter means; means for coupling the summing means to the second heater; first and second sample-and-hold means; second switch means for alternately connecting the first and second sample-and-hold means to the integrator-inverter means output in synchronism with said first switch means; and means coupled to the first and second sample-and-hold means for providing the difference between the two sample-and-hold outputs.
Claim 3
Dependent Claim
19 words
An apparatus as claimed in claim 1 in which the thermal converter means is a differential multijunction thermal converter.
Claim 4
Dependent Claim
17 words
An apparatus as claimed in claim 1 in which the second voltage is a precision dc voltage.
Claim 5
Dependent Claim
39 words
An apparatus as claimed in claim 3 which further includes a series connected limiting amplifier and full-wave operational rectifier means having an input coupled to the dc voltage and an output coupled to the input of the summing means.
Claim 6
Dependent Claim
24 words
An apparatus as claimed in claim 1 in which further includes generator means for providing switching signals to the first and second switch means.
Claim 7
Dependent Claim
18 words
An apparatus as claimed in claim 5 in which said first and second switch means are mosfet switches.
Claim 8
Dependent Claim
52 words
An apparatus as claimed in claim 6 in which said first voltage is an ac voltage and said generator means includes a zero crossing detector coupled to the ac voltage; and a timing generator coupled to the detector to provide timing signals to the mosfet switches in synchronism with the ac voltage.
Claim 9
Dependent Claim
22 words
An apparatus as claimed in claim 6 in which amplifier means is coupled between the first switch means and the first heater.
Claim 10
Dependent Claim
59 words
An apparatus as claimed in claim 1 in which the means for providing the difference between the two sample-and-hold circuits includes a unity gain inverter means coupled to the first sample-and-hold means; a third amplifier means coupled to the outputs of the inverter means and the second sample-and-hold means; and zero-centre meter means coupled to the third amplifier means.
Claim 11
Independent Claim
160 words
An apparatus for comparing a first voltage to a dc voltage comprising: a differential thermal converter means having a first and a second heater; first switching means for alternately connecting the first voltage and the dc voltage to the first heater; a series connected limiting amplifier and full wave operational rectifier means having an input coupled to the dc voltage and an output coupled to the second heater; second amplifier means coupled to the thermal converter output; integrator-inverter means coupled to the second amplifier means; means for summing the output of the second amplifier means and the integrator-inverter means; means for coupling the summing means to the input of the second amplifier means; first and second sample-and-hold means; second switch means for alternately connecting the first and second sample-and-hold means to the output of the integrator-inverter means in synchronism with said first switch means; and means coupled to the sample-and-hold means for providing the difference between the two sample-and-hold outputs.
Claim 12
Independent Claim
160 words
An apparatus for comparing a first voltage to a dc voltage comprising: a differential thermal converter means having a first and a second heater; first switching means for alternately connecting the first voltage and the dc voltage to the first heater; a series connected limiting amplifier and full wave operational rectifier means having an input coupled to the dc voltage and an output coupled to the second heater; second amplifier means coupled to the thermal converter output; integrator-inverter means coupled to the second amplifier means; means for summing the output of the second amplifier means and the integrator-inverter means; means for coupling the summing means to the input of the second amplifier means; first and second sample-and-hold means; second switch means for alternately connecting the first and second sample-and-hold means to the output of the integrator-inverter means in synchronism with said first switch means; and means coupled to the sample-and-hold means for providing the difference between the two sample-and-hold outputs.
Claim 13
Dependent Claim
19 words
An apparatus as claimed in claim 10 in which the thermal converter means is a differential multijunction thermal converter.
Claim 14
Dependent Claim
23 words
An apparatus as claimed in claim 10 which further includes generator means for providing switching signals to the first and second swtich means.
Claim 15
Dependent Claim
18 words
An apparatus as claimed in claim 12 in which said first and second switch means are mosfet switches.
Claim 16
Dependent Claim
54 words
An apparatus as claimed in claim 13 in which said first voltage is an ac voltage and said generator means includes - a zero crossing detector coupled to the ac voltage; and - a timing generator coupled to the detector to provide timing signals to the mosfet switches in synchronism with the ac voltage.
Claim 17
Dependent Claim
22 words
An apparatus as claimed in claim 13 in which amplifier means is coupled between the first switch means and the first heater.
Claim 18
Dependent Claim
60 words
An apparatus as claimed in claim 10 in which the means for providing the diffErence between the two sample-and-hold circuits includes - a unity gain inverter means coupled to the first sample-and-hold means; a third amplifier means coupled to the outputs of the inverter means and the second sample-and-hold means; and zero-centre meter means coupled to the third amplifier means.
References Cited (Backward Citations)
US1121835A
Cited
US2896165A
Cited
US2805394A
Cited
US3213364A
Cited
US3399348A
Cited
US3521164A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-14 | 1978-04-15 | 1978-10-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-14 | 1982-04-15 | 1982-10-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-14 | 1986-04-15 | 1986-10-15 | $7700.00 | Window Closed / Lapsed |