US3786350A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Linear input ohmmeter
Assignee: Sycon Corp
•
Filing: 1972-08-21
•
Granted: 1974-01-15
•
Expires: 1992-08-21
Abstract
Abstract A digital ohmmeter having a differential amplifier with a capacitor connected between the output and the inverting input to form an integrator. A source of DC voltage is connected to a series circuit including the unknown resistor and to a switch which selectively connects the source to a second series circuit, an intermediate point of which is connected to the inverting terminal of the amplifier. The unknown resistor is connected to the noninverting input. The output of the amplifier is connected to logic circuit and counting means of the type used in dual slope integrating digital voltmeters, and others such as voltageto-frequency converters, with the logic means having an output to control the switch means. The switch is open for a fixed interval and closed for a variable interval, which variable interval is counted as a measure of the input resistance. In this embodiment, the two series resistance circuits form a bridge when the switch is closed. In a second embodiment an additional switch connects the second series circuit to ground when it is disconnected from the source. In either embodiment the resistance value is linearly proportional to the length of the variable interval of time multiplied by a constant, the constant being determined by the fixed resistors in the two series circuits.
Inventors
- 👤 I Munt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 00:33
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; H; H03; H03M; H03M1/00; H03M1/12; H03M1/50; H03M1/52
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
147 words
Apparatus for providing an output signal the magnitude of which is linearly representative of the value of an unknown resistance comprising the combination of a source of voltage; means for defining a measurement interval; resistor circuit means for connecting said source of voltage to one terminal of the unknown resistance to be measured during at least part of said measurement interval; a resistive circuit of known value; switch means for selectively completing a circuit between said voltage source and one end of said resistive circuit; integrator circuit means having input terminals connected to said one terminal of the unknown resistance and to an intermediate point of said resistive circuit for combining the signals developed at those points during a measurement interval; and means connected to said means for defining a measurement interval for responding to the output of said integrator circuit means for controlling said switch means.
Claim 2
Dependent Claim
147 words
Apparatus for providing an output signal the magnitude of which is linearly representative of the value of an unknown resistance comprising the combination of a source of voltage; means for defining a measurement interval; resistor circuit means for connecting said source of voltage to one terminal of the unknown resistance to be measured during at least part of said measurement interval; a resistive circuit of known value; switch means for selectively completing a circuit between said voltage source and one end of said resistive circuit; integrator circuit means having input terminals connected to said one terminal of the unknown resistance and to an intermediate point of said resistive circuit for combining the signals developed at those points during a measurement interval; and means connected to said means for defining a measurement interval for responding to the output of said integrator circuit means for controlling said switch means.
Claim 3
Dependent Claim
37 words
Apparatus according to claim 1 and further comprising means for displaying a value proportional to the output of said integrator circuit means at the end a measurement interval as a representation of the resistance of the unknown.
Claim 4
Dependent Claim
169 words
A digital ohmmeter comprising the combination of a differential amplifier having a capacitor connected between the output and an input thereof to form an integrating amplifier; a source of DC potential; circuit means forming a bridge circuit comprising a first resistor; terminals connectable to an unknown resistor to place the unknown resistor in series circuit relationship with said first resistor between said source and ground; second and third resistors connected in series circuit relationship; and switch means operable to selectively connect disconnect said second and third resistors to said source and ground; circuit means connecting the junction between said first and unknown resistors to one input of said differential amplifier and the junction between said second and third resistors to the other input of said amplifier; timing means for controlling the operation of said apparatus; means responsive to said timing means and to the output of said amplifier for producing a digital drive signal linearly representative of the value of the unknown resistor; and means for displaying said value.
Claim 5
Dependent Claim
169 words
A digital ohmmeter comprising the combination of a differential amplifier having a capacitor connected between the output and an input thereof to form an integrating amplifier; a source of DC potential; circuit means forming a bridge circuit comprising a first resistor; terminals connectable to an unknown resistor to place the unknown resistor in series circuit relationship with said first resistor between said source and ground; second and third resistors connected in series circuit relationship; and switch means operable to selectively connect disconnect said second and third resistors to said source and ground; circuit means connecting the junction between said first and unknown resistors to one input of said differential amplifier and the junction between said second and third resistors to the other input of said amplifier; timing means for controlling the operation of said apparatus; means responsive to said timing means and to the output of said amplifier for producing a digital drive signal linearly representative of the value of the unknown resistor; and means for displaying said value.
Claim 6
Dependent Claim
44 words
An ohmmeter according to claim 3 wherein said switch means includes first switch means for selectively connecting said second resistor to said source; and second switch means for connecting said third resistor to ground only when said second resistor is disconnected from said source.
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) | 1977-01-14 | 1977-07-16 | 1978-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-14 | 1981-07-16 | 1982-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-14 | 1985-07-16 | 1986-01-15 | $7700.00 | Window Closed / Lapsed |