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Sensor FAQs

What is “GMR”?
Giant magnetoresistors, where resistance changes due to conduction electrons scattering at interfaces. GMR is an effect of spintronics, which utilizes electron spin rather than electron charge. The technology is smaller, more sensitive, and lower power than conventional semiconductors. In awarding the 2007 Nobel Prize in Physics for GMR, the Nobel Committee said, “GMR can be considered one of the first real applications of the promising field of nanotechnology.” This video has illustrative animations.

Why GMR sensors?
The advantages of GMR sensors are summarized with the four Bs: Boxes (smaller devices); Bits (more sensitive); Batteries (power as low as nanowatts); and Bullet-proof (extremely reliable).

What types of GMR sensors does NVE offer?
Analog sensors, digital sensors, current sensors, angle sensors, and GT™ (gear tooth) rotary sensors.

What’s the difference between tesla, gauss, and oersteds?
Tesla and gauss are units of magnetic flux density. One tesla is 10,000 gauss. Oersteds are units of magnetizing field strength. Oersteds and gauss have a one-to-one correspondence in air.

What’s the difference between a magnetometer and gradiometer?
A magnetometer sensor measures magnetic field strength. A gradiometer measures the magnetic field strength gradient, or change, over a distance.

What’s your most sensitive sensor?
The AAH002. AAH-Series high-sensitivity magnetic sensors have an amazing minimum sensitivity of 11 mV/V-Oe (more than one thousand times better than a typical Hall-effect sensor).

What’s the sensor minimum supply voltage?
Analog sensors can run on any voltage because they have no active components. For digital switch sensors, AHL-Series Low-Voltage Digital Sensors and certain AFL-Series Digital Sensors operate as low as 0.9 V supply voltage.

What packages are available?
The most popular packages are MSOPs, SOICs, 2.5 mm TDFNs, and 1.1 mm ULLGAs.

What’s the smallest package?
We offer sensors in a 1.1 mm square, leadless “ULLGA” package. If that’s still too big, we offer bare die for chip-on-board construction.

How far away can your sensors detect a magnet?
An inch or so, depending on many factors. Unless you’re dying to use multivariate calculus and Maxwell’s equations, we have a simple flux density calculator spreadsheet for calculating magnetic fields versus distance.

I what to determine the current through a PCB trace. How can I figure out the magnetic field generated?
That’s even worse math than the magnet question above, so we have a spreadsheet for estimating the magnetic field generated by current flowing through a circuit-board trace.

Where can I get magnets for experiments and prototypes?
Popular magnets are in-stock on NVE’s online store, and several sensor evaluation kits include magnets.

How can I try NVE sensors?
Distributors such as Digi-Key stock a wide variety of NVE sensors. The NVE Online Store has no minimum order and $9.95 flat-rate shipping to North America. Sensor Evaluation Kits are available to try out a variety of parts.

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