Direct reading inductance meter
OwnerJames C. Administrator of the National Aeronautics and Space Administration, with respect to an invention of Fletcher, Richard B. Kolblyinventors
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Abstract
A direct reading inductance meter is comprised of a crystal oscillator for generating a reference frequency f.sub.r and an LC tuned oscillator for generating an initial frequency f.sub.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.sub.x, a difference frequency (f.sub.r -f.sub.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.
Claims9
Apparatus for direct measurement of the inductance exhibited by an element which is essentially inductive in a range below 3.mu.H, comprising
- means for generating a first alternating signal at a stable reference frequency, f.sub.r,
- means for generating a second alternating signal at an initial frequency, f.sub.o, substantially equal to said reference frequency, said second signal generating means including an LC circuit tuned to resonance at said initial frequency f.sub.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.sub.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.sub.r and f.sub.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.
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 3.mu.H 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.
Dependencies are inferred from the claim text.