How BKWAT Measures Your Data
BKWAT rings, watches and fitness trackers use a handful of sensors to turn signals from your body into the numbers you see in the app. This page explains what each sensor does, how it works and which devices have it, so you know what your data means and where its limits are.
The sensors inside BKWAT devices
| Sensor | What it tracks | How it works | Found in |
|---|---|---|---|
| Optical heart-rate sensor (PPG) | Heart rate, HRV, blood oxygen (SpO₂), stress and sleep | LEDs shine light into your skin and a light sensor measures the small changes in reflected light each time your heart pumps blood. The app turns that pattern into heart rate and related trends. | All BKWAT smart rings, smartwatches and fitness trackers. The TK36 uses four light sensors (4PD) instead of one. |
| ECG electrodes | ECG recordings | Metal electrodes on the device pick up the electrical signal of your heartbeat. You start a recording in the app and complete the circuit by touching the electrode with a finger of your other hand while you sit still. | Smartwatches: E400, E600, ET473, ET573, ET456, ET491, F100, Health Smartwatch 3, S26, S191. Fitness trackers: TK35 Pro, TK36, E910. Ring: V80. |
| Air-pump cuff | Blood pressure, for daily reference | A small airbag built into the strap inflates around your wrist like a traditional cuff and measures the pressure as it releases. | S26 and S191 smartwatches |
| Optical blood-pressure estimate | Blood pressure trends, for daily reference | Some models estimate blood pressure trends from the optical (PPG) signal. These are estimates, not cuff measurements, and can differ from a blood pressure monitor. | Listed under Health tracking on each product page |
| Temperature sensor | Skin temperature trends | Measures the temperature of your skin, not your core body temperature. Changes against your own normal range are more useful than a single reading. | Rings: K80, BKD1. Many smartwatches and the TK35 Pro, TK36 and E910 bands |
| EDA sensor | Electrodermal activity (stress response) | Measures small changes in the electrical properties of your skin, which shift as your body responds to stress. | V80 ring |
| Motion sensor | Steps, distance, calories, sport modes, sleep and wake times, gestures | Detects movement and orientation. It counts steps, recognizes activity and helps tell when you fall asleep and wake up. | All BKWAT wearables |
| Built-in GPS | Route, distance and pace outdoors | Receives satellite signals directly, so you can leave your phone at home. The DM56, DM59 and DM76 use two frequencies (L1 + L5), which helps keep tracking steady near tall buildings and trees; the DM58 uses one (L1). | DM56, DM58, DM59 and DM76 smartwatches |
| Connected GPS | Route, distance and pace outdoors | Uses your phone’s GPS through the app, so keep your phone with you during the workout. | K80 ring and Screenless Health Smart Band |
How often readings are taken
- Automatic tracking: heart rate, steps and sleep are recorded automatically through the day and night. How often depends on the model and the settings in its app; many apps let you choose the interval.
- On-demand readings: ECG and air-pump blood pressure are taken when you start a measurement in the app or on the watch.
- Example: the V80 ring analyzes sleep overnight from midnight to 6am and updates every five minutes.
What can affect your readings
- Fit: a ring or strap that is loose lets light in and moves around. Wear it snug but comfortable.
- Movement: keep still during ECG, blood pressure and blood oxygen readings.
- Cold hands or low circulation: less blood flow near the skin makes optical readings harder.
- Skin and sensor: tattoos under the sensor, lotion or a dirty sensor window can weaken the signal. Wipe the sensor regularly.
- Consistency: trends are most useful when you wear the device every day and night.
About accuracy
BKWAT devices are consumer wellness products, not medical devices. Their readings are meant to help you notice patterns in your daily routine, and they can differ from medical equipment. We only publish accuracy figures when we have test results to support them. If you have a health concern, talk to a doctor and use a medical device.
Learn more
- ECG smartwatches explained: how they work
- How smart rings track sleep
- Which app does my device use?
- Smart ring size guide
Health data is for general wellness reference only and is not intended to diagnose, treat or prevent any disease.