What does 5 ATM really mean?
Rated for 50 meters of static water pressure in a lab. Fine for showers, rain and pool swimming, but the sudden pressure of diving or high-speed water sports exceeds it. It is a sealing spec, not a diving depth.
Hardware teardown, interactive
A $59.99 band with no screen still packs a dedicated ECG chip, a contact thermistor, a MEMS accelerometer, Bluetooth 5.3 and 5 ATM sealing. Drag the exploded view, then tap a layer to see what each part actually does.
Tap any label above. The matching layer lights up here and the page scrolls to its full explanation.
3D view unavailable on this device; the diagram above shows the five stacked layers of the band.
Every heartbeat starts with an electrical pulse. Two stainless electrodes (one under your wrist, one you touch with a finger) close a circuit across your chest and record that voltage directly, producing the classic PQRST waveform below. Optical PPG sensors on cheaper bands only watch blood flow with green light; ECG sees the electrical timing itself, which is why it can flag irregular rhythms.
Negative Temperature Coefficient means resistance falls as skin gets warmer. The band passes a tiny current through the pad, measures resistance, and converts it to temperature. Because the change is steep and predictable around body temperature, an NTC is cheap, tiny and accurate exactly where it matters. Drag the slider to move along the curve.
A microscopic silicon mass on springs shifts when the band moves; capacitance changes on three axes become live X, Y, Z acceleration values. Drag the chip to tilt it and watch gravity redistribute across the bars. Step counting is just peak detection: each stride creates a spike, and the firmware counts spikes with the right rhythm and size.
3D view unavailable; use the bars below with the step animation to see how motion becomes data.
Rated for 50 meters of static water pressure in a lab. Fine for showers, rain and pool swimming, but the sudden pressure of diving or high-speed water sports exceeds it. It is a sealing spec, not a diving depth.
Lower power draw for longer battery life, better coexistence with crowded Wi-Fi and other radios, and more efficient connection scheduling so syncing your data costs less energy.
Two spring pins snap onto magnets in the correct orientation every time. No fragile port to let water in, which is a big reason the band can hold its 5 ATM seal.