Wearable-ready sensor combines ECG, optical heart rate monitoring within single module

By Dave Muoio
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Austin, Texas-based semiconductor producer Silicon Labs has announced a new line of optical biometric sensors that promise more fleshed out heart rate monitoring and lower power consumption for consumer-grade wearables. By combining optical heart rate monitoring alongside ECG measurements within a single unit, the company says their new Si117x and Si118x sensor modules offer an easier way for device manufacturers to include more accurate and diverse monitoring in smart watches, patches, or other wearable devices seeking to track a user’s biometrics.

“In any of these consumer-driven devices, power, cost, and size are always an issue. Just being able to take two devices and fit them into one, you get the benefit of being able to bring price down and power down,” Sid Sundar, sensors product manager at Silicon Labs, told MobiHealthNews. “There is also a lot of value in making these measurements together, and what our chip does is allows you to very easily make them together and figure out very small time differences between them accurately.”

Sundar explained that many of the past few years’ health and fitness-focused wearables primarily take heart rate measurements using optical light sensors alone. Combining this type of sensor with even a single input channel ECG, however, can allow a device to measure additional metric types, such as pulse wave velocity or pulse volume. However, having both of these sensors running independently introduces new design challenges for a device manufacturer.

“When you make these measurements on two different sensors, you always have the problem of both sensors making their measurements on their own time,” Sundar said. “Usually people have to keep a processor alive to do that, or burn extra power, or do a lot of post processing. We kind of bypass a lot of that by having them built into the same sensor.”

Combining both sensor types within a single module not only allows for a less bulky final product, it also allows a device to run continuously without needing to recharge or be turned off. This particular benefit is becoming increasingly important as devices seek to capture and describe a user’s entire day.

“We realize that as this industry evolves, there’s a lot more data that can be gleaned by looking at information continuously,” Sundar said. “For example, if I just sample my heart rate on demand, that can be of limited value — maybe you can figure out what your heart rate is during a certain exercise. But if you’re continuously monitoring someone’s heart rate in the background, you can analyze that data over time and figure out more useful information such as heart rate variability, maybe what your resting heart rate is, an understanding of what implications they have for cardiac health … and be able to do interventions before things reach a critical point.”

Outside of energy reduction and improved monitoring, Sundar stressed that the new offerings are designed as a complete, easy-to-integrate chip to reduce the burden on manufacturers looking to add heart rate monitoring to their consumer device. Specifically, the module includes a motion-compensating heart rate algorithm, the option for built-in LEDs (depending on the model), and a variety of of development kits and other tools to streamline the development process.

“What we’ve seen is that there are a lot of device makers who are looking to add these capabilities, but these are outside of general consumer device capabilities. Most people aren’t used to doing optical design, or having to worry about measuring light accurately, and having to develop algorithms to determine heart rate,” Sundar said. “We’re capable of doing complete end-to-end solutions, and reducing the time to market for a lot of these customers.”