US3746880A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Circuit for determining the state of a dc isolated switch
Assignee: Yokogawa Electric Corp
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Filing: 1971-11-08
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Granted: 1973-07-17
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Expires: 1991-11-08
Abstract
Abstract A switch and a device for monitoring the open or closed state of the switch are conneted by a DC isolation circuit including an isolating transformer, a capacitor in the transformer primary circuit with the switch connected across the capacitor, and, in the transformer secondary circuit, an alternating pulse signal source to charge the capacitor through the transformer. In this circuit, the impedance reflected into the transformer secondary winding varies in accordance with the open or closed state of the switch. To permit the state of the switch to be accurately determined, the circuit disconnects the alternating signal pulse source from the transformer secondary while applying a read signal pulse to the transformer secondary to determine the reflected impedance, thereby eliminating errors arising from superposition of the read signal on the alternating signal without necessitating synchronization of the two pulse signals.
Inventors
- 👤 T Iritani
- 👤 Y Kumagai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 07:51
CPC Classifications
G; G08; G08C; G08C19/00; G08C19/30
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
150 words
A circuit for determining the open or closed state of a switch while maintaining the switch in DC isolation, the circuit including an isolating transformer with a primary circuit including a charging element interconnected with said switch, and a secondary circuit including an alternating signal source for charging said charging element through the transformer according to the open or closed state of the switch whereby the impedance reflected into said transformer secondary winding varies according to the open or closed state of the switch, characterized by means for applying a read signal to the transformer secondary winding to determine the impedance reflected therein from said primary circuit, thereby to determine the open or closed state of the switch, and means for disconnecting said alternating signal source from said transformer secondary while applying said read signal, thereby eliminating reading errors due to superposition of the read signal on the alternating signal
Claim 2
Dependent Claim
150 words
A circuit for determining the open or closed state of a switch while maintaining the switch in DC isolation, the circuit including an isolating transformer with a primary circuit including a charging element interconnected with said switch, and a secondary circuit including an alternating signal source for charging said charging element through the transformer according to the open or closed state of the switch whereby the impedance reflected into said transformer secondary winding varies according to the open or closed state of the switch, characterized by means for applying a read signal to the transformer secondary winding to determine the impedance reflected therein from said primary circuit, thereby to determine the open or closed state of the switch, and means for disconnecting said alternating signal source from said transformer secondary while applying said read signal, thereby eliminating reading errors due to superposition of the read signal on the alternating signal
Claim 3
Dependent Claim
19 words
A circuit as claimed in claim 1 wherein said alternating signal and said read signal are both pulse signals.
Claim 4
Dependent Claim
48 words
A circuit as claimed in claim 1 wherein said means for disconnecting the alternating signal source comprises means for providing a blanking signal embracing the read signal and, gate means connecting said alternating source to said transformer secondary winding, said gate means being inhibited by said blanking signal.
Claim 5
Dependent Claim
32 words
A circuit as claimed in claim 3 in which said blanking signal begins in advance of said read signal to permit transients to settle, and ends after said read signal is completed.
Claim 6
Dependent Claim
26 words
A circuit as claimed in claim 3 wherein said read signal and said alternating signal are applied to the transformer secondary winding through NOR gate means.
Claim 7
Dependent Claim
95 words
A circuit as claimed in claim 1 wherein said means for applying a read signal to the transformer secondary comprises an output terminal, coincidence gate means connecting said output terminal and said transformer winding, means applying the read signal to the coincidence gate means, and means applying the read signal to at least a portion of the transformer secondary winding, whereby a signal will appear at said output terminal only when the impedance of said transformer secondary winding is low in response to the closed state of said switch and only during a read signal.
Claim 8
Dependent Claim
97 words
A circuit as claimed in claim 6 wherein said means for disconnecting the alternating signal source comprises means for providing a blanking signal embracing the read signal and gate means inhibited by the blanking signal for connecting the alternating signal with said transformer secondary winding, and wherein the means applying the read signal to the coincidence gate means includes second coincidence gate means and means for applying the blanking signal to the second coincidence gate means, whereby said read signal will be applied to said first coincidence gate means only during the existence of a blanking signal.
Claim 9
Dependent Claim
68 words
A circuit as claimed in claim 1 wherein said alternating signal source is a pulse oscillator, said charging element is a capacitor, said switch is connected to discharge said capacitor when in a closed state, and said primary circuit includes a diode in series with said primary winding and capacitor, whereby said capacitor is charged by said alternating pulse signal when said switch is in an open state.
Claim 10
Independent Claim
122 words
A method for determining the open or closed state of a switch while maintaining the switch in DC isolation, comprises connecting said switch with a charging element, in a primary circuit, isolating said primary circuit by means of an isolation transformer from a secondary circuit, applying an alternating signal in said secondary circuit so as to charge the charging element in the primary circuit according to the condition of the switch, applying a read signal in said secondary circuit so as to measure the impedance reflected through from said primary circuit, and disconnecting said alternating signal from said secondary circuit while said read signal is being applied, thereby eliminating reading errors due to superposition of the read signal with the alternating signal.
Claim 11
Independent Claim
122 words
A method for determining the open or closed state of a switch while maintaining the switch in DC isolation, comprises connecting said switch with a charging element, in a primary circuit, isolating said primary circuit by means of an isolation transformer from a secondary circuit, applying an alternating signal in said secondary circuit so as to charge the charging element in the primary circuit according to the condition of the switch, applying a read signal in said secondary circuit so as to measure the impedance reflected through from said primary circuit, and disconnecting said alternating signal from said secondary circuit while said read signal is being applied, thereby eliminating reading errors due to superposition of the read signal with the alternating signal.
References Cited (Backward Citations)
US3346855A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-16 | 1977-01-15 | 1977-07-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-16 | 1981-01-15 | 1981-07-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-16 | 1985-01-15 | 1985-07-17 | $7700.00 | Window Closed / Lapsed |