Design win; ST accelerometer & MCU drive wearable heart-rate monitor

December 10, 2014 // By Graham Prophet
STMicroelectronics provides the MEMS accelerometer and the STM32L microcontroller into what is claimed as smallest wearable heart-rate monitor, from PulseOn. The motion-sensing and data-processing chips provide precision and performance with tiny dimensions and low energy budget.

Aimed at the fitness market, the wrist-worn device from PulseOn (Espoo, Finland) is simple and intuitive to use. It provides accurate continuous heart-rate measurement without the need for a chest strap, and its algorithms transform the heart-rate data into meaningful personalised feedback for each individual.

ST's low-power, high-performance MEMS accelerometer maintains the PulseOn heart-rate measurement accuracy and reliability at the level delivered by an electrocardiogram, as proven by extensive scientific testing under all possible scenarios and conditions, from physical inactivity up to the highest exertion levels in various cardio-intensive activities.

The accelerometer tracks hand motion and vibrations to eliminate the noise in optical blood-flow detection. The PulseOn monitor can distinguish between the signal that represents the actual heart pulse and which is just noise caused by hand movements. The accelerometer also determines the wearer’s level of physical activity.

The STM32L microcontroller functions reliably on minimal energy use; PulseOn’s developers optimised the application’s power consumption using the STM32L’s ultra-low-power modes. “The superior precision and performance of ST chips have enabled us to apply the strictest scientific standards to the PulseOn heart-rate measurement technology, producing reliable results that includes the beat-to-beat accuracy during rest,” said Jari Nousiainen, Head of Engineering, PulseOn. “Equally important, the minuscule dimensions and energy budget of ST ICs have been a competitive advantage.”