Optical sensor targets fitness tracking

Optical sensor targets fitness tracking
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Osram Opto Semiconductors has developed an integrated optical sensor specially designed for heart rate monitoring. The component is used in fitness trackers, smart watches and other wearables.
By eeNews Europe


The SFH 7051 sensor consumes little power to maximize battery life.

The SFH 7051 consists of a large-format photo diode and three green LEDs with a wavelength of 530 nm. The device is used for monitoring heart rate by measuring the volume of blood passing through blood vessels. The device works by shining light on the surface of the skin. Different amounts of this light are absorbed by blood and the surrounding tissue. The light not absorbed is reflected to the detector. With its green emission spectrum the SFH 7051 is ideal for measuring the pulse rate at the wrist.

The green emitter chips of the SFH 7051 are based on the latest high-efficiency UX:3 chip technology from Osram Opto Semiconductors. The sensor uses three of these chips so that they can be operated at the optimum current of 20 mA. At this operating current the efficiency of the emitters is particularly high. Overall, SFH 7051 produces an optical output of 3 x 3.4 mW at a current of 20 mA and a voltage of 3.2 V. The low power consumption of the component means long battery life in the device. With an area of only 1.7 mm2, the photodiode is small enough to enable the sensor to be compact, but sensitive enough to offer the required signal quality. Its low capacitance of only 11 picofarads ensures short switching times and high measuring frequency.

SFH 7051 is the second integrated optical sensor from Osram for fitness tracking applications. In 2014, the company launched the SFH 7050, a multifunction sensor for measuring heart rate and the oxygen content of blood.

Users have a choice between the multifunction SFH 7050 and the SFH 7051 which is optimized for pulse rate monitoring. The housing dimensions of the two sensors are identical.


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