New thin sensor developed for SpO2 measurement

ams, a supplier of high performance sensor solutions, has introduced a thin dedicated sensor for blood oxygen saturation (SpO₂) measurement, bringing the capability to remotely monitor this vital sign to small consumer products, as well as to medical devices such as patches and oximeters.

The performance of the new AS7038RB also means it is suitable for applications in remote diagnostic equipment, such as disposable patches used for SpO₂ and electro-cardiogram (ECG) measurement in hospital emergency rooms.

A growing body of evidence suggests that low SpO₂ is an early symptom of the COVID-19 disease before the onset of breathing difficulty in some at-risk patients. The development of a wearable SpO₂ measurement device based on the AS7038RB can be used remotely and therefore help in the treatment of people infected with the SARS-CoV-2 virus.

Wim Renirie, vice president and general manager for the accessory and wearable solutions at ams, said: “The introduction of the AS7038RB marks another ams breakthrough in technology for remote diagnostics. ams is working actively with a range of partners to develop innovative solutions for the testing and diagnosis of COVID-19. The AS7038RB offers an additional diagnostic tool, enabling the creation of wearable and disposable equipment for monitoring blood oxygen saturation accurately and safely, without requiring the presence of a medical practitioner.”

The AS7038RB’s combination of small size, integrated functionality, and a high-performance signal chain makes it ideal for OEMs that are developing innovative applications for health monitoring in space-constrained consumer or medical products. The sensor, housed in a package with a footprint of 3.70mm x 3.10mm and which is just 0.65mm thin, integrates a highly sensitive photodiode, four LED drivers, an analogue front end, and a sequencer. It is supplied with application software for SpO₂and heart rate measurement. The analogue front end also supports concurrent ECG measurement complying with the requirements of the IEC 6060-2-47 medical standard.

The accuracy of the AS7038RB’s SpO₂ measurements, very closely matching the outputs from medical-grade pulse oximeters used in hospital testing facilities, is in part due to the unique on-wafer interference filter technology developed by ams. The filter enables the AS7038RB to capture optical signals in the 590nm-710nm and near infrared (800nm-1050nm) wavelength bands of interest for SpO₂measurement, while blocking interference from ambient light at other wavelengths.

The AS7038RB’s provision of drivers for up to four external LEDs gives OEMs the flexibility to place the LEDs in the best position for the application. This means LED placement can be optimized for the different skin thicknesses and bone structure at the wrist, chest, forehead, finger, etc.

The sensor’s sensitivity and signal-to-noise ratio enable it to operate with a low optical power output from the LEDs. The integrated LED drivers provide for adjustment of the drive current, so the OEM can balance system power consumption and measurement performance, helping to extend run-time between battery charges in devices such as earbuds, which contain a small battery power source.