Apple Watch Series 6 can measure the oxygen saturation of the user's blood, so the users may better understand their overall fitness and wellness.

To compensate for natural variations in the skin and improve accuracy, the Blood Oxygen sensor employs four clusters of green, red, and infrared LEDs, along with the four photodiodes on the back crystal of Apple Watch, to measure light reflected back from blood, the company demonstrated.

Apple Watch uses a custom algorithm built into the Blood Oxygen app to measure blood oxygen between 70 percent and 100 percent.

The new Apple Watch's new hardware improvements include a faster S6 System in Package (SiP) and an always-on altimeter.

Its new operating system "watchOS 7" also brings new features such as Family Setup, sleep tracking, automatic handwashing detection, new workout types, and the ability to curate and share watch faces, the company said.

Using a new dual-core processor based on A13 Bionic in iPhone 11, the upgraded S6 SiP runs up to 20 percent faster while maintaining the same 18-hour battery life, according to Apple.

The new Apple Watch will be available on Friday, Sept 18, starting at $399.