US4786859A
Expired / Lapsed
US
⏱️ 0.0 years remaining
RMS measuring apparatus for AC/DC voltages
Assignee: National Research Council Canada
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Filing: 1987-05-29
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Granted: 1988-11-22
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Expires: 2007-05-29
Abstract
Abstract A true RMS instrument using a multijunction thermal converter with two beaters automatically determines and displays the RMS value of an unknown voltage using two steps or modes. In an AC mode, the unknown voltage is attenuated and balanced in the thermal converter with a DC voltage. DC voltage is stored in digital form in a first latch. In the DC mode, the unknown attenuated voltage is replaced by a chopped DC voltage which is then balanced with the DC voltage obtained in the AC mode. The unknown voltage is determined by decoding the contents of a second lath which controls the chopped DC voltage.
Inventors
- 👤 Rejean Arseneau
- 👤 John J. Zelle
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 07:54
CPC Classifications
G; G01; G01R; G01R19/00; G01R19/02
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
289 words
An apparatus for automatically measuring the true RMS value of an input signal, comprising: a thermal converter means having a first heater, a second heater and a converter output terminal, an attenuator means for receiving the input signal and producing an attenuated input signal, an electronic switch means connected between the attenuator means and the first heater, an integrating means connected to the output terminal for amplifying and integrating a converter output signal from the converter output terminal, a counter means connected to the integrating means for producing a counter output in response to the converter output signal, a first latch means connected between the counter means and the second heater for applying a first latch output to the second heater in response to the counter output, a second latch means connected to the counter means for producing, in response to the counter output, a second latch output, a chopper means connected between the second latch means and the electronic switch means for applying a chopper output to the electronic switch means in response to the second latch output, and a display means connected to the counter means, in that: the said electronic switch means alternately applies the attenuated input signal and the chopper output to the first heater; the first latch means latches the first latch output when the converter output signal indicates that the attenuated input signal and the first latch output are balanced; the second latch means latches the second latch output when the converter output signal indicates that the chopper output and the first latch output are balanced; and the display means displays the counter output which is indicative of the true RMS value of the input signal when the second latch means is latched.
Claim 2
Independent Claim
289 words
An apparatus for automatically measuring the true RMS value of an input signal, comprising: a thermal converter means having a first heater, a second heater and a converter output terminal, an attenuator means for receiving the input signal and producing an attenuated input signal, an electronic switch means connected between the attenuator means and the first heater, an integrating means connected to the output terminal for amplifying and integrating a converter output signal from the converter output terminal, a counter means connected to the integrating means for producing a counter output in response to the converter output signal, a first latch means connected between the counter means and the second heater for applying a first latch output to the second heater in response to the counter output, a second latch means connected to the counter means for producing, in response to the counter output, a second latch output, a chopper means connected between the second latch means and the electronic switch means for applying a chopper output to the electronic switch means in response to the second latch output, and a display means connected to the counter means, in that: the said electronic switch means alternately applies the attenuated input signal and the chopper output to the first heater; the first latch means latches the first latch output when the converter output signal indicates that the attenuated input signal and the first latch output are balanced; the second latch means latches the second latch output when the converter output signal indicates that the chopper output and the first latch output are balanced; and the display means displays the counter output which is indicative of the true RMS value of the input signal when the second latch means is latched.
Claim 3
Dependent Claim
16 words
The apparatus according to claim 1 wherein the thermal converter is a differential multijunction thermal converter.
Claim 4
Dependent Claim
61 words
The apparatus according to claim 2, further comprising: a preset means connected between the attenuator means and the counter means for applying a preset signal, in response to the attenuated input signal, to the counter means, and an error monitor means connected between the integrating means and the counter means for producing a preset enable signal which enables the counter means.
Claim 5
Dependent Claim
21 words
The apparatus according to claim 3, further comprising a DC precision reference for calibrating the first and the second latch means.
Claim 6
Dependent Claim
41 words
The apparatus according to claim 4 wherein the integrating means includes a voltage-to-frequency converter, the first and the second latch means are each provided with a digital-to-analog converter, and the display means includes a decoding means for decoding the converter output.
Claim 7
Dependent Claim
22 words
The apparatus according to claim 5 wherein the attenuator means comprises a plurality of attenuators for different ranges of the input signal.
Claim 8
Dependent Claim
16 words
The apparatus according to claim 6 wherein the integrating means further comprises a chopper stabilized amplifier.
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) | 1991-11-22 | 1992-05-23 | 1992-11-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-11-22 | 1996-05-23 | 1996-11-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-11-22 | 2000-05-23 | 2000-11-22 | $7700.00 | Window Closed / Lapsed |