Magnetometer readout
The magnetometer reports magnetic field strength in microtesla on three axes. Away from interference the total reads somewhere around 25 to 65 µT, which is the Earth's own field.
| Sensor used | Magnetometer |
|---|---|
| Unit | Microtesla (µT) |
| Useful range | Earth's field is about 25–65 µT depending on latitude |
| Cannot do | Measure fields safely near strong magnets, where the sensor saturates |
The mechanism, not the marketing.
The sensor measures magnetic flux density along three perpendicular axes. Combining them gives both a total magnitude and a direction, which is what makes the compass possible.
Anything magnetic changes the local total. Moving the phone toward a fridge magnet, a speaker or a steel beam raises it, often dramatically.
What a phone cannot do here.
- The phone's own components contribute a constant offset, and cases with magnets or metal plates add a large one.
- Strong magnets saturate the sensor, so the number stops rising and can be meaningless — and very strong magnets can leave a lasting offset that requires recalibration.
- Readings vary with orientation, so comparisons are only meaningful if the phone is held consistently.
What is a normal magnetometer reading?
Away from metal and magnets, the total field should sit somewhere between about 25 and 65 µT. Where you are on Earth determines where in that range.
My reading is very high — is that dangerous?
No. Everyday fields near speakers, magnets and appliances are far below any level associated with health effects. A high reading means something magnetic is nearby, nothing more.
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