Tiny Heart Rate Sensor For Fitness Wearables


OSRAM Opto Semiconductors offers an integrated Optical sensor to simplify heart rate or pulse rate measurements. The sensor is intended to be used in mobile devices, such as smart watches and fitness armbands.

Integrated sensor SFH 7050 features three emitters and a photodiode in a compact size measuring just 4.7 x 2.5 x 0.9 mm.

SFH 7050 contains three light emitting diodes with different wavelengths. A built-in photodetector receives the reflected optical signals and is separated from the emitters by an opaque barrier.

The three emitters built into the sensor have wavelengths of 530 nm (green), 660 nm (red) and 940 nm (infrared). These enable the pulse at the wrist or fingertip and the oxygen content of the blood at the fingertip to be measured.

By controlling each of the emitters individually, the sensor can be used for different applications. Green light can be used for measuring the pulse at the wrist. Red or infrared emitters are generally used for measuring the pulse at the finger as they can then also measure the oxygen content of the blood (pulse oximetry).

Its noteworthy that each of the three emitters feature narrow spectral bandwidths of around 30 nm. The red LED has a specified wavelength tolerance of only ±3 nm to allow precise measurements.

“As far as measuring the oxygen content of blood is concerned, the absorption of light by blood depends largely on the wavelength of the light. The small tolerances of the red LED mean that precise measurements can be achieved with the new sensor”, explained Dr. Jörg Heerlein, Senior Manager Product Marketing at Osram Opto Semiconductors.

This Optical Sensor Is a Blessing For Robot Makers

The compact photodiode integrated in the sensor has an active surface of 1.3 mm x 1.3 mm. Not only is the diode very sensitive to light, but also enables an extremely compact sensor.

The infrared LED can also be used in combination with the photodiode as a proximity sensor to start or stop the measurement automatically as soon as the sensor touches or is removed from the skin.

Osram plans to present the sensor at electronica 2014 (hall A3, booth 107) which will take place in Munich from November 11 to 14, 2014.

For further details, view the full Press release.


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