In a new support document for the first time Apple is information on details of the integrated in the Apple Watch Heart Rate Monitor. In addition to the explanation of the operation of the sensor Apple are also tips for accurate pulse measurements.

In the Apple support document describes the operation of the sensor located on the underside of the Apple Watch. During the day, Apple’s Smart Watch is distinguished by default every 10 minutes on the pulse. To set the clock in the Sport mode, the pulse is continuously measured and displayed on the screen.


With the help of green LEDs and infrared light, the clock measures the pulse. Blood is red because it absorbs reflects red light and green light. The heartbeat increases the blood flow so that even more will absorb green light. Between the heart beats, it is less. With the help of the fast flashing LEDs – hundreds of times per second – can the Apple Watch calculate the heart rate.

By default, uses the Apple Watch infrared light for the measurements during the day. If the data are not precise enough, the green LEDs are used. The Apple Watch automatically adjusts the intensity of the LEDs and the sampling rate.

Fasten seat belts

If the results of a pulse monitor not be accurate, it may be, among other things, that the Apple Watch is worn too loose. As a first step, therefore, the bracelet should be streamlined.

The possibility of pulse measurement but also depends on the skin type or temperature. Therefore, it may in some cases led to the Apple Watch can see no pulse.

Some sports are better suited to further pulse measurement than others: Rhythmic movements such as running or cycling give more accurate results than tennis or boxing. In such cases, the Apple Watch therefore, with external pulse monitors, such as chest straps are connected via Bluetooth.

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