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How SamaWritten works

Wear it. Forget it.
It's watching for you.

Three things, every second of every day. Sensing. Understanding. Acting. No app to open, no button to press.

01Always sensing

Five sensors. All the time.

Heart rhythm, blood oxygen, blood pressure, skin, movement. Sampled continuously. No buttons. You forget you're wearing it.

02AI understands

On-device AI reads the signals

All five signals fused on the device — nothing leaves your wrist by default. Catches arrhythmias as they happen. Predicts heart failure up to 6.5 days early.

03Gets you help

Alerts for help from your wrist

Vibrates first to confirm it's not a false alarm. Silent for 30 seconds? It alerts your contacts and sends GPS + ECG over 2G.

How a MAX30001
becomes a vital sign.

The AFE on SamaBeat's wrist module is the Analog Devices MAX30001 — one part doing ECG and bioimpedance. The BioZ channel injects a known AC current, watches the voltage that comes back, and ships 20-bit complex impedance samples to the MCU. Everything downstream — respiration, stroke volume, cuffless BP — is derived from that single stream.

01stage

Inject

Programmable AC current source drives BIP / BIN electrodes. 50 kHz sinusoid at 80 µA peak-to-peak — below sensation, safe under IEC 60601.

02stage

Sense

Voltage drop is read on a separate BIPS / BINS sense pair (tetrapolar). Electrode-skin impedance drops out — only tissue Z remains.

03stage

Amplify

Instrumentation amp with programmable gain (10–80 V/V), bandpass-tuned around the injection frequency to reject line noise and motion artifact.

04stage

I/Q demodulate

On-chip synchronous demodulator multiplies the signal by in-phase and quadrature copies of the injection clock — gives real (R) and reactive (X) baseband channels.

05stage

Σ-Δ ADC

20-bit sigma-delta converter on each baseband channel, decimated to 32 / 64 / 128 sps. 32-deep FIFO; MCU pulls over SPI at every DRDY interrupt.

06stage

Translate

MCU converts counts → ohms: Z = counts × V_LSB / I_inject. At 80 µA + 20 V/V gain, ~6.7 mΩ/LSB. |Z| = √(R² + X²); φ = atan2(X, R).

Wire-formatPOST /api/bioz/ingest
{
  "deviceId": "sb-0042",
  "injectHz": 50000,
  "injectUaPp": 80,
  "samples": [
    { "ts": 1717030001000, "zMagOhm": 462.3, "zPhaseDeg": 6.41,
      "deltaZmOhm": -12.7, "quality": 0 }
  ]
}
Respiration

Bandpass ΔZ 0.1–0.5 Hz → breaths/min from thoracic impedance swing.

Stroke volume

Pulse-band ΔZ 0.5–5 Hz, Kubicek formula — feeds cuffless BP fusion.

Hydration

Low-frequency |Z| inversely tracks total body water; trended for fluid status.

Lead-off

LOFF flags from the AFE gate every sample — bad-contact data never reaches the model.

Edge cases, covered

Wi-Fi down at 3am?
SamaBeat still alerts for help.

The hard part of an emergency device isn't the happy path. It's the five questions every family asks before they'll trust it.

False alarm?

30 seconds to dismiss before it alerts. One touch. No panic.

No cell coverage?

Data queues locally, syncs the moment coverage returns. Zero heartbeats lost.

Battery low?

Emergency alerts keep working down to 5% battery. Everything else gets paused first.

Subscription lapsed?

Emergency alerts always work. No subscription, no exceptions.

Travelling abroad?

Built-in eSIM roams across supported markets. Your guardian crosses borders with you.

Read the science →

Ready to put a guardian on your wrist?

Reserve early access. We will reach out once your cohort opens.

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