HydroGuard’s arm-worn hydration prototype

Field notes

The band estimates hydration through upper-arm impedance: one electrode pair injects a small alternating current and another measures the resulting voltage. The first board was deliberately 100 × 100 mm for accessible test points, while the planned second board is roughly 30 × 21 mm and uses an E73 nRF52840 module. The team says it will add motion and humidity sensing to distinguish hydration changes from sweat, movement, and a shifted strap.