US4045728A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Direct reading inductance meter
Assignee: National Aeronautics and Space Administration
•
Filing: 1976-04-15
•
Granted: 1977-08-30
•
Expires: 1996-04-15
Abstract
Abstract A direct reading inductance meter is comprised of a crystal oscillator for generating a reference frequency f r and an LC tuned oscillator for generating an initial frequency f o which, when mixed with the reference, produces a difference equal to zero. Upon connecting an inductor of small unknown value in the LC circuit to change its resonant frequency to f x , a difference frequency (f r -f x ) is produced that is very nearly a linear function of the inductance of the inductor. The difference frequency is measured and displayed on a linear scale in units of inductance.
Inventors
- 👤 with respect to an invention of Fletcher James C. Administrator of the National Aeronautics and Space Administration
- 👤 Richard B. Kolbly
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 03:36
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/26; G01R27/2611
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
180 words
Apparatus for direct measurement of the inductance exhibited by an element which is essentially inductive in a range below 3μH, comprising means for generating a first alternating signal at a stable reference frequency, f r , means for generating a second alternating signal at an initial frequency, f o , substantially equal to said reference frequency, said second signal generating means including an LC circuit tuned to resonance at said initial frequency f o to control the frequency of said second signal, said LC circuit having an inductance at least approximately five times greater than said element, switching means for connecting said element to be measured to said LC circuit to change the resonant frequency thereof to a frequency f x , means for mixing said first and second signals to obtain a third signal of a frequency equal to the difference between the frequencies f r and f x , and means for measuring the frequency of said third signal and for displaying the value of said element as a linear, function of the frequency of said third signal.
Claim 2
Dependent Claim
180 words
Apparatus for direct measurement of the inductance exhibited by an element which is essentially inductive in a range below 3μH, comprising means for generating a first alternating signal at a stable reference frequency, f r , means for generating a second alternating signal at an initial frequency, f o , substantially equal to said reference frequency, said second signal generating means including an LC circuit tuned to resonance at said initial frequency f o to control the frequency of said second signal, said LC circuit having an inductance at least approximately five times greater than said element, switching means for connecting said element to be measured to said LC circuit to change the resonant frequency thereof to a frequency f x , means for mixing said first and second signals to obtain a third signal of a frequency equal to the difference between the frequencies f r and f x , and means for measuring the frequency of said third signal and for displaying the value of said element as a linear, function of the frequency of said third signal.
Claim 3
Dependent Claim
69 words
Apparatus as defined in claim 1 wherein said frequency measuring means is comprised of means for generating a pulse of predetermined pulse width for each cycle of said third signal, and a lossy-integration and display means for so integrating each of said pulse of predetermined pulse width as to produce a display of the value of said element as a linear function of the rate of said pulses integrated.
Claim 4
Dependent Claim
17 words
Apparatus as defined in claim 2 wherein said lossy-integration and display means is comprised of an ammeter.
Claim 5
Dependent Claim
162 words
A direct reading inductance meter comprising a reference oscillator for generating a reference signal at a stable frequency, an LC tuned oscillator for generating a second signal at a frequency equal to said reference frequency as determined by an included LC tuned circuit, a mixer for mixing said second signal with said reference signal to obtain an output signal at a difference frequency equal to the difference between said reference frequency and said second frequency, means for connecting an element of unknown inductance of some unknown value less than about 3μH to said LC tuned circuit having an inductance at least approximately five times greater than the unknown element thereby to shift said second frequency by an amount approximately in linear proportion to said unknown value of inductance, and means for measuring the frequency of said output signal with said element connected to said LC tuned circuit for determining said unknown value of inductance as a linear function of said difference frequency.
Claim 6
Dependent Claim
162 words
A direct reading inductance meter comprising a reference oscillator for generating a reference signal at a stable frequency, an LC tuned oscillator for generating a second signal at a frequency equal to said reference frequency as determined by an included LC tuned circuit, a mixer for mixing said second signal with said reference signal to obtain an output signal at a difference frequency equal to the difference between said reference frequency and said second frequency, means for connecting an element of unknown inductance of some unknown value less than about 3μH to said LC tuned circuit having an inductance at least approximately five times greater than the unknown element thereby to shift said second frequency by an amount approximately in linear proportion to said unknown value of inductance, and means for measuring the frequency of said output signal with said element connected to said LC tuned circuit for determining said unknown value of inductance as a linear function of said difference frequency.
Claim 7
Dependent Claim
154 words
Apparatus as defined in claim 4 wherein said frequency measuring means is comprised of a separate pulse shaping amplifier for each of said reference and second signals to produce a reference train of pulses and a second train of pulses from said reference signal and second signal, respectively, one pulse in each train for each cycle of the signal being amplified, a flip flop adapted to be set in response to a particular point in each pulse of one of said trains of pulses to a state determined by the voltage level of the other of said trains of pulses, a multivibrator responsive to the output of said flip-flop to produce an output pulse of predetermined duration for each cycle of said flip-flop, and means for integrating output pulses from said multivibrator with a lossy integrator, thereby producing a signal the average amplitude of which is proportional to the unknown inductance of said element.
Claim 8
Dependent Claim
33 words
Apparatus as defined in claim 5 wherein said last named means is comprised of means for rectifying said output pulses, and an ammeter connected to measure the current output of said rectifying means.
Claim 9
Dependent Claim
41 words
Apparatus as defined in claim 4 wherein said LC tuned circuit is comprised of a circuit of inductance and capacitance in parallel, and said unknown element is connected by said connecting means in series with the inductance of said parallel circuit.
Claim 10
Dependent Claim
153 words
Apparatus as defined in claim 7 wherein said frequency measuring means is comprised of a separate pulse shaping amplifier for each of said reference and second signals to produce a reference train of pulses and a second train of pulses from said reference signal and second signal, respectively, one pulse in each train for each cycle of the signal being amplified, a flip-flop adapted to be set in response to a particular point in each pulse of one of said trains of pulses to a state determined by the voltage level of the other of said trains of pulses, a multivibrator responsive to the output of said flip-flop to produce an output pulse of predetermined duration for each cycle of said flip-flop, and means for integrating output pulses from said multivibrator with a lossy integrator, thereby producing a signal the average amplitude of which is proportional to the unknown inductance of said element.
Claim 11
Dependent Claim
33 words
Apparatus as defined in claim 8 wherein said last named means is comprised of means for rectifying said output pulses, and an ammeter connected to measure the current output of said rectifying means.
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) | 1980-08-29 | 1981-02-28 | 1981-08-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-08-29 | 1985-02-28 | 1985-08-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-08-29 | 1989-02-28 | 1989-08-30 | $7700.00 | Window Closed / Lapsed |