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We're demonstrating a TMR guitar pickup using
the world's most sensitive TMR magnetometers the ALT021-10E
ALT021-10E are ultra- sensitive, ultraminiature TMR magnetometers that can detect permanent magnets
at large distances the small remnant field, ferrous materials such as guitar strings, and even
slight changes in Earth magnetic field down to 0.1 microtesla. We wired six sensors in
parallel--one for each string--and we're detecting the guitar string movement without external permanent
magnets. The strings themselves are magnetic enough to get a voltage signal from the ALT021.
We used our SR-560 as a differential amplifier for AC- coupling the sensors. Unlike inductive coils, NVE's
TMR magnetometers are DC-correct and have a flat frequency response from DC up to 100 kilohertz.
The signal splits from the SR-560 so we can observe the waveform
on an oscilloscope while playing the sound through a small Vox combo amp.
We tuned this guitar by ear before shooting the video. Let's check how we did on the scope.
Not too bad. Could you tell the difference?
Now for the most important part: the tone test. The pickup is located between the
neck position and the middle position, so we expect a warmer, mellower tone.
♪♪
We'll check a Fender Standard Telecaster for comparison.
Here's the wiring schematic. The bulky inductive coil is wrapped around a set
of magnetic pole pieces positioned under each string. We're using the signal from
the microphone to view the waveform on the oscilloscope. First the neck pickup:
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Then the bridge pickup:
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We'll have to admit defeat today, but we'll be back in future episodes with improved
designs so stay tuned. To be fair, guitar amplifiers are designed to amplify inductive coils, which
involves significant frequency coloring to get a classic guitar tone, TMR guitar pickups might
need to be altered purposely. But for practical applications the advantages of an ultra-sensitive,
ultraminiature, DC correct, flat-frequency- response sensor are numerous. Small changes in
Earth magnetic field can be detected, enabling detection of parked cars or buried objects.
Ferrous metal with small remnant magnetic fields can be detected without adding external permanent
magnets, which means the sensors can be used to detect proximity to potentially dangerous
industrial equipment or to detect motion and speed as an alternate to inductive pickups.
Small currents can be detected non-contact and at large distances. The sensors can also be
used as low-power, non-contact data receivers for programming devices since the sensors can detect
DC magnetic fields. They can also be used as a low- power watchdogs for battery-powered electronics.
These use cases are commonly found in industrial, defense, and medical applications.
Key ALT021 features include: High sensitivity, Ultra miniature package size DC correct field,
detection, flat frequency response, excellent temperature stability, and customizable
resistance--from microamps for battery power to low impedance for high-speed applications.
NVE Corporation is your leader in spintronics, offering magnetic sensors and digital isolators
manufactured in the USA. Click, email, or call for more information. And like and
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