Proving the Business Case for the Internet of Things

AMS optical heart rate monitor can be integrated into wearables

Steve Rogerson
October 6, 2015
Austria Microsystems (AMS) has launched an optical heart rate monitor that can be integrated into wearable devices.
The AS7000 incorporates an integrated optical sensor module accompanied by software to provide accurate optical heart rate measurements and heart rate variation (HRM and HRV) readings.
The first member of a family of health and fitness technology aimed at wearable devices, the AS7000 is housed in a 6.1 by 4.1 by 1.0mm package, and is claimed to be the industry’s first complete integrated health and fitness device for wearables intended to be worn constantly, at rest and when exercising.
The introduction of the module raises the prospect of devices such as fitness bands as well as sports and smart watches allowing for accelerated design cycles and replacing the cumbersome, uncomfortable electro-cardiogram (ECG) chest strap in lifestyle, fitness and health monitoring applications.
The module includes the LEDs, photo-sensor, analogue front end (AFE) and controller as well as application software required to implement an accurate optical HRM and HRV fitness band product. It also enables skin temperature and skin resistivity measurements by providing interfaces to external sensors.
Drawing on its expertise in optical sensing in mobile devices, AMS provides OEMs with electrical, mechanical and optical design guidelines to enable them to quickly realise implementation. These guidelines address critical opto-mechanical difficulties such as the design and material of the wrist strap and housing, and specific optical design considerations such as the air gap and glass thickness.
Operation is based on photoplethysmography (PPG), an HRM method that measures the pulse rate by sampling light modulated by the blood vessels, which expand and contract as blood pulses through them. Unlike existing optical AFEs, which produce raw PPG readings, the AS7000 integrates a digital processor that implements algorithms developed by AMS. These convert the PPG readings into digital HRM and HRV values.
When it is paired with an external accelerometer, these algorithms also filter out motion artefacts attributable to the beating of the heart, which interfere with PPG readings. Combined with the low noise and high sensitivity of the analogue circuitry, this means the module can maintain high accuracy whether the user is resting or exercising.
The low-power design is particularly suited to applications in fitness bands, smart watches, sports watches, and devices in which board space is limited and in which users look for extended, multi-day intervals between battery recharges.
“Unique AMS innovations which reduce noise, compensate for motion artefacts and conserve energy have resulted in a breakthrough for the health-monitoring and fitness-monitoring markets,” said Ronald Tingl, biosensors senior marketing manager at AMS. “The AS7000 is ideally suited to customers seeking a total solution that enables a quick time to market when adding health and fitness features to their wearables.”
A complete HRM and HRV wristband demonstration kit is available on request. Containing a fitness band-mounted AS7000, it uploads its HRM and HRV readings via a Bluetooth interface board to any smartphone or tablet running the Android operating environment. An AMS-developed heart rate app presents HRM and HRV readings and allows for real-time logging of all the data.