What EMF actually measures
An EMF meter (or your phone's magnetometer, which is what SpiritMesh uses) measures the strength of the local magnetic field in microteslas (µT). Earth's natural field is roughly 25–65 µT depending on location. Anything moving electricity nearby — wiring, motors, transformers, your phone — adds to it.
Why baseline is everything
A reading of '50 µT, oh no!' means nothing without a baseline. If your room sits at 48 µT, then 50 is normal. If it sits at 28 and suddenly hits 50, that's a 22 µT spike — interesting. SpiritMesh's calibration ritual exists exactly for this. Always calibrate.
Common environmental causes
Refrigerators, microwaves, HVAC compressors, fuse boxes, dimmer switches, LED drivers, smartphones, laptops, chargers, Wi-Fi routers, and old CRT TVs. If you're getting consistent readings near a wall, the wiring inside that wall is probably the cause.
Reading spikes well
A real anomaly tends to: rise quickly from baseline, persist for multiple seconds, and not correlate with someone moving past appliances. Single-frame jumps are usually you bumping the phone or the sensor recalibrating. Multi-second sustained anomalies away from electronics are the ones worth investigating further.