Hall measurement system with rotary magnet
AssigneeInternational Business Machines Corporation
InventorsTayfun Gokmen, Oki Gunawan
Life of this patent
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Abstract
One or more embodiments are directed to a motor configured to rotate at least one magnet at a first frequency, a sensor configured to generate a reference signal of the at least one magnet's rotation, and a lock-in detection system configured to receive the reference signal, supply an excitation current at a second frequency to a device under test, measure a voltage from the device under test and demodulate the second frequency, and demodulate the first frequency from the measured voltage using the reference signal to obtain a Hall voltage associated with the device under test.
Claims20
A method of implementing a Hall effect measurement, the method comprising:
- applying an excitation current (I) at a first frequency (f1) to a device under test;
- concurrently with applying the excitation current, rotating at least one magnet at a second frequency (f2) in proximity to the device under test so as to generate a magnetic field (B);
- providing, to a first lock-in amplifier, a first stage input Hall voltage signal (V1) generated by the excitation current and the magnetic field, and proportional to the expression:
- (I0 cos ω1t)×(B0 cos ω2t);
- wherein I0 is an amplitude of the excitation current I, B0 is an amplitude of the magnetic field B, ω1=2πf1 and ω2=2πf2;
- filtering out, with the first lock in amplifier, the first frequency component f1 of the first stage input Hall voltage signal so as to generate a first stage output Hall voltage signal (VO1) proportional to the expression:
- I0B0 cos ω2t;
- providing, to a second lock-in amplifier, the first stage output Hall voltage signal and filtering out the second frequency component f2 so as to generate a second stage output Hall voltage signal (VO2) proportional to the expression:
- I0×B0.
A system for implementing a Hall effect measurement, comprising:
- a first lock-in amplifier configured to apply an excitation current (I) at a first frequency (f1) to a device under test;
- a motor configured to rotate at least one magnet at a second frequency (f2) in proximity to the device under test so as to generate a magnetic field (B), concurrently with application of the excitation current;
- the first lock-in amplifier further configured to receive, a first stage input Hall voltage signal (V1) generated by the excitation current and the magnetic field, and proportional to the expression:
- (I0 cos ω1t)×(B0 cos ω2t);
- wherein I0 is an amplitude of the excitation current I, B0 is an amplitude of the magnetic field B, ω1=2πf1 and ω2=2πf2;
- the first lock in amplifier further configured to filter out the first frequency component f1 of the first stage input Hall voltage signal so as to generate a first stage output Hall voltage signal (VO1) proportional to the expression:
- I0B0 cos ω2t;
- and
- a second lock-in amplifier configured to receive the first stage output Hall voltage signal and filter out the second frequency component f2 so as to generate a second stage output Hall voltage signal (VO2) proportional to the expression:
- I0×B0.
Dependencies are inferred from the claim text.