Non-invasive core body temperature sensor employs Nordic Semiconductor wireless connectivity to deliver real time performance insights to athletes

Swiss sensor technology company, greenteg AG, has launched what it says is the world's first non-invasive, wearable core body temperature sensor. The 'CORE 2' sensor clips to a heart rate monitor strap and is placed on the skin, from where it uses a proprietary heat flux sensor to measure thermal energy transfer from the body to the environment. The device is powered by Nordic Semiconductor's multiprotocol nRF52840 SoC, and is designed to be used by athletes of all levels to improve performance.

Alongside the heat flux sensor, the CORE 2 device integrates a precision skin temperature sensor that together helps the user understand their thermophysiologial state. The nRF52840 SoC features a powerful Arm® Cortex™ M4 CPU with floating point unit (FPU), which is capable of the processor-intensive computations required by advanced wearable designs.

Multiprotocol connectivity

The SoC's multiprotocol radio provides Bluetooth® LE wireless connectivity to the 'CORE' smartphone app. From the app the user can see an accurate calculation of their core body temperature-a deep internal temperature that reflects the thermal state of the entire body, including organs and tissues-as well as their 'Heat Strain Index' score, a real time measure of how hard your body is working to stay cool. The app also provides advanced analytics such as a 'Heat Adaptation Score', helping athletes monitor their heat training progress and optimize performance in hot conditions. In addition to smartphone connectivity, the nRF52840 SoC also provides Bluetooth LE or ANT+ wireless connectivity to popular sports technology platforms for a better in-workout experience.

"Combined with machine learning algorithms and additional inputs, the data from CORE 2 provides real time monitoring, tracking, and post-workout analysis," says Ross McGraw, Global VP and Head of CORE. "It enables athletes to optimize performance through guided heat training, and maintain control over thermal strain, helping them train hot and race cool.

Fully-automatic power management

The CORE 2 device is powered by a small, rechargeable Li-Poly cell, providing between one and two weeks use between recharge depending on use pattern and battery health. The extended battery life is made possible, in part, by the nRF52840 SoC's ultra-low power consumption and fully-automatic power management system.

"Small size and a light weight are key for CORE 2, so we actively looked for an SoC with low power consumption and arrived at the nRF52840," says Michele Zahner, Head of R&D at greenteg. "The other important factors were a large Flash memory capacity to locally store data for several days and good chip availability.

"Nordic's large availability of reference designs and technical documentation was also very helpful and allowed us to de-risk development at a very early stage."

• About greenteg AG
• About CORE
• About Nordic Semiconductor