Ferrum: Stud Finder & Metal

Ferrum is an honest, calibrated measuring instrument built on your iPhone's magnetometer. It starts measuring the second you open it — continuously, with no timers, no upgrade prompts, and no subscription. WHY FERRUM EXISTS Wall scanners on the App Store interrupt your measurement to sell you something, charge weekly for a sensor your phone already has, or dress up the Earth's own magnetic field as a "detection". Ferrum does none of that. You pay once. There are no ads, no accounts, and the app never connects to the internet. CALIBRATED, NOT GUESSING The Earth's magnetic field runs 25-65 µT, and your phone adds a bias of its own. Ferrum measures that background first, then shows you only the change — the number that actually means something. Recalibrate any time with one tap. FOUR MODES, ONE ENGINE - Stud - find the screws that hold a wooden stud in place, with a narrow threshold tuned for sharp local peaks. - Wire - find live AC wiring by its mains signature, not by field strength, so a steady piece of steel never masquerades as a live cable. Works on both 50 Hz and 60 Hz mains, with no setting to choose. - Metal - maximum sensitivity to ferromagnetic mass: steel framing, pipes, rebar. - Recovery - for lost things. MAX HOLD keeps the peak reading and the audio is at its loudest, for rings in the grass, buried boundary pins and time capsules. Geiger-style ticks speed up as you close in, with haptic feedback in the same rhythm so you can work in a noisy room or with the sound off. The screen stays awake while you measure. HONEST ABOUT PHYSICS A magnetometer senses ferromagnetic metal — iron and steel — and the changing fields of live wiring. It cannot see gold, silver, copper, aluminum or plastic, and it cannot tell you how deep something sits. Ferrum says so plainly on its Learn screen, along with how to actually find a wooden stud (you find the screws), why readings drift, and a trick for tracing a circuit that is switched off. No fear content. No invented "risk levels". PRIVACY Data Not Collected. No analytics, no identifiers, no network access at all. Not a substitute for a professional scanner where safety matters. Always verify before drilling.