US4408282A
Expired / Lapsed
US
⏱️ 0.0 years remaining
AC Resistance measuring instrument
Assignee: United States Department of Energy
•
Filing: 1981-04-22
•
Granted: 1983-10-04
•
Expires: 2001-04-22
Abstract
Abstract An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument.
Inventors
- 👤 Peter J. Hof
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 03:49
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/22; G01N27/223; G01R; G01R27/00; G01R27/02
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
201 words
An instrument for measuring the impedance of an electrical device through a transmission line having one end connected to said electrical device and the other end connected to said instrument comprising: signal generating means for generating an excitation signal having a particular wave shape; compensation circuit means for compensating for the capacitance of the transmission line coupled between said signal generating means and said other end of the transmission line, said compensation circuit means, the transmission line, and said electrical device being responsive to said excitation signal to develop an output signal at the other end of the transmission line corresponding to the voltage across the transmission line and said electrical device; and signal processing means coupled to said other end of the transmission line for sampling said output signal and comparing the wave shape of the said signal with said particular wave shape, said signal processing means further being connected to said compensation circuit means and acting to control the impedance of said compensation circuit means to bring the wave shape of the output signal within a preselected correspondence with said particular wave shape wherein the output signal is indicative of the impedance of the transmission line and the device.
Claim 2
Dependent Claim
201 words
An instrument for measuring the impedance of an electrical device through a transmission line having one end connected to said electrical device and the other end connected to said instrument comprising: signal generating means for generating an excitation signal having a particular wave shape; compensation circuit means for compensating for the capacitance of the transmission line coupled between said signal generating means and said other end of the transmission line, said compensation circuit means, the transmission line, and said electrical device being responsive to said excitation signal to develop an output signal at the other end of the transmission line corresponding to the voltage across the transmission line and said electrical device; and signal processing means coupled to said other end of the transmission line for sampling said output signal and comparing the wave shape of the said signal with said particular wave shape, said signal processing means further being connected to said compensation circuit means and acting to control the impedance of said compensation circuit means to bring the wave shape of the output signal within a preselected correspondence with said particular wave shape wherein the output signal is indicative of the impedance of the transmission line and the device.
Claim 3
Dependent Claim
25 words
The instrument of claim 1 wherein said signal processing means further acts to measure said sampled output signal for calculating the impedance of the device.
Claim 4
Dependent Claim
20 words
The instrument of claim 2 further comprising delay means coupled to said signal processing means for displaying said calculated impedance.
Claim 5
Dependent Claim
70 words
The instrument of claim 1 further comprising range select means including a plurality of resistors connected in parallel with said compensation circuit means for limiting the amplitude of the output signal, said signal processing means further being connected to said range select means and acting to control said range select means wherein an appropriate resistor range is selected to bring the amplitude of the output signal within a preselected value.
Claim 6
Dependent Claim
39 words
The instrument of claim 4 wherein said compensating circuit means comprises a plurality of capacitors and a plurality of switching devices, each associated with a different one of said capacitors and each individually operable by said signal processing means.
Claim 7
Dependent Claim
13 words
The instrument of claim 5 wherein said capacitors are binary weighted in value.
Claim 8
Dependent Claim
39 words
The instrument of claim 4 wherein said range select means comprises a plurality of resistors and a plurality of switching devices, each associated with a different one of said resistors and each individually operable by said signal processing means.
Claim 9
Dependent Claim
22 words
The instrument of claim 7 further comprising an additional range resistor connected between said signal generating means and said range select means.
Claim 10
Dependent Claim
13 words
The instrument of claim 8 wherein said signal generating means comprises a microprocessor.
Claim 11
Dependent Claim
15 words
The instrument of claim 8 wherein said particular wave shape is a bipolar square wave.
Claim 12
Dependent Claim
20 words
The instrument of claim 10 wherein said preselected value is 50% to 90% of the amplitude of the excitation signal.
Claim 13
Dependent Claim
34 words
The instrument of claim 11 wherein said signal processing means further comprises timing means for generating a timing signal which establishes the frequency of the excitation signal and which establishes output signal sampling rates.
Claim 14
Dependent Claim
30 words
The instrument of claim 12 wherein the output signal is sampled near the leading and trailing edges of the positive and negative half cycles of the bipolar square wave signal.
Claim 15
Dependent Claim
23 words
The instrument of claim 13 wherein said signal processing means averages the signal samples for a plurality of cycles of the excitation signal.
Claim 16
Dependent Claim
15 words
The instrument of claim 14 wherein the frequency of the excitation signal is 50 Hz.
Claim 17
Dependent Claim
13 words
The instrument of claim 1 wherein the instrument power source is a battery.
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) | 1986-10-03 | 1987-04-04 | 1987-10-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-10-03 | 1991-04-04 | 1991-10-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-10-03 | 1995-04-04 | 1995-10-04 | $7700.00 | Window Closed / Lapsed |