GhostScope What is a normal EMF reading on a phone, and what causes spikes?
On a phone's magnetometer, a reading of a few tens of µT with nothing nearby is normal: it is mostly the Earth's magnetic field. After you tap Calibrate, a normal reading is close to 0, and anything that climbs into the tens or hundreds of µT is almost always a magnet, a speaker, steel or electronics close to the phone.
Why the reading is never zero at first
The Earth is a big magnet. Wherever you stand, its field reaches your phone at a strength of roughly 25 to 65 µT depending on where on the planet you are, and steel in the building and nearby electronics add to it. A phone magnetometer measures all of that together.
So with no calibration, GhostScope typically sits at two or three LEDs in a quiet room. That is not a haunting. It is the planet. Tap Calibrate with the phone held still and that background becomes 0.0, which makes real changes easy to spot.
Normal EMF levels in microtesla on the GhostScope meter
Here is how the app's 5-LED scale maps to the value it shows. These are the app's display bands, not health limits.
| LEVEL | Reading in µT | Same in mG | What it usually means after calibrating |
|---|---|---|---|
| 0 | under 10 | under 100 | Nothing new near the phone |
| 1 | 10 to under 25 | 100 to under 250 | Something magnetic or metal a little closer, or the phone turned |
| 2 | 25 to under 50 | 250 to under 500 | An uncalibrated room reading, or electronics close by |
| 3 | 50 to under 80 | 500 to under 800 | A speaker, laptop or steel object within a short distance |
| 4 | 80 to under 120 | 800 to under 1200 | Close to a magnet or speaker; the default spike alert triggers |
| 5 | 120 or more | 1200 or more | Almost touching a magnet, MagSafe accessory or speaker |
What is a high EMF reading?
In GhostScope, a high reading is simply one at or above your spike alert threshold, set in Settings. The default is 80 µT: at that point the app logs an EMF Spike, vibrates, and plays a short sound if Audio cues is on. It logs at most one spike per second.
You choose the threshold in Settings, from 40 to 150 µT in steps of 5. A low threshold catches small changes but fires often. A high one only fires right next to strong magnets. Most people should keep it at 80, the default, since anything lower can trigger an alert every time the phone passes something like a laptop charger.
What the app will not tell you is whether a level is safe. It is not an exposure meter, and the magnetometer does not measure the alternating fields or radio waves that exposure guidelines talk about.
What causes EMF spikes on a phone?
- Magnets: fridge magnets, magnetic phone cases, MagSafe chargers and wallets, magnetic clasps on bags and covers.
- Speakers and headphones, which contain strong permanent magnets.
- Steel: radiators, filing cabinets, bed frames, door frames, tools.
- Laptops, tablets and other devices with magnets or motors.
- Moving or turning the phone itself, which changes how the Earth's field hits the sensor.
- Sensitivity boost: at ×1.4 every change looks 40% bigger than at ×1.0.
Microtesla to milligauss
Handheld meters often use milligauss. The conversion is exact: 1 µT = 10 mG, so multiply µT by 10. In GhostScope, go to Settings, then Display, then Units, and pick mG (milligauss); the live number, gauge and PEAK switch over.
| µT | mG |
|---|---|
| 0.1 | 1 |
| 1 | 10 |
| 10 | 100 |
| 48.3 | 483 |
| 80 | 800 |
| 150 | 1500 |
Only the display changes. The spike threshold, the radar's boost text and the numbers in the Hunt Log stay in µT.
How to set the spike alert
- Tap the Settings tile on the home screen.
- Under Sensitivity, drag the slider labelled 'Spike alert at 80 µT' to the level you want; the label follows the value.
- Set the slider labelled 'Boost ×1.0' if you want the meter more or less sensitive. Free users can go from ×0.5 to ×1.4; above that needs Pro.
- Under Feedback, turn Haptics and Audio cues on or off.
- Go back to the EMF Meter, tap Start Hunt and Calibrate.
Example: calibrated at 48.3 µT, you hold the phone near a speaker and the raw reading is 131.7 µT. At boost ×1.0 the meter shows 83.4 µT, LEVEL 4. With the alert at 80 µT a spike is logged; at 90 µT it is not.
Questions and answers
What is a normal EMF reading for a house on a phone?
Is 50 µT a lot?
Why does the reading drift when I stand still?
Can I change what counts as a spike?
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More GhostScope guides
- How to use your iPhone as an EMF meter
- Using the EVP recorder during a ghost hunt
- How to ghost hunt with your phone, from start to log
- Yes or no pendulum on your phone: how the answer is made
- Do ghost detector apps really work? What is real and what is effect
- Does iPad have a magnetometer?
- Can iPhone detect magnets?
- Run a Halloween Ghost Hunt With Your iPhone
- All questions about GhostScope
- Back to GhostScope