ams OSRAM (AMS), a global leader in optical solutions, has introduced a three-channel UV-A/B/C sensor, the AS7331, which brings UV dosage and exposure monitoring within reach of cost-sensitive devices for home use. The AS7331 is the first CMOS sensor from ams OSRAM to measure radiation at UV-C as well as UV-A and UV-B wavelengths.  

The AS7331, which is aimed at the consumer and industrial markets, offers very high sensitivity and high dynamic range. Customers also benefit from the cost efficiency of CMOS device fabrication. 

High sensitivity of up to 421 counts/(µW/cm2) in the UV-A range means that the AS7331 can detect biofluorescence – a function required in water quality monitoring – or partial discharges in electric motors. Low-cost UV sensor chips on the market today are not sensitive enough to detect such weak UV signals. High dynamic range of 3.43E+10 gives product designers the flexibility to implement UV monitoring under both strong and weak sources of radiation. At 125µs, minimum measurement time is four times faster than the next best UV sensor currently available in the consumer market. 

Markus Busz, senior product manager for spectral sensing at ams OSRAM, said: ‘The introduction of the AS7331 means that high-sensitivity UV dosage monitoring is now affordable enough to be built into devices for home use such as robotic floor cleaners, coffee brewing machines and home, water, and air purifiers. It fills a new position in the market between low-cost UV sensors which offer very low sensitivity, and high-performance, lab-grade UV sensors which are too expensive for devices intended for home use.’  

The sensor is also suitable for applications such as UV curing and phototherapy. Markus Busz added: ‘Today, consumer disinfection and purification products typically include no UV-C monitoring capability because of the high cost of existing UV-C sensors. In the absence of accurate dosage information, these products are set to produce very high radiation and treatment times to ensure that the minimum necessary dosage is exceeded. This wastes power and accelerates the aging of UV light sources and irradiated materials. The launch of the AS7331 enables manufacturers to accurately limit emissions from a UV-C light source to the minimum necessary, improving performance and giving better value to the end user.’  

By combining UV-A, UV-B and UV-C monitoring in a single device, the AS7331 also enables manufacturers to save space and reduce bill-of-materials cost in multi-function applications. For instance, in water purification systems the AS7331 can analyze the quality of the water by measuring the absorption of UV-A light. It can then measure UV-C radiation to check that a sufficient dose is administered to fully purify the water. 

Precise optical performance characteristics 

The AS7331 is a three-channel sensor which uses interference filters to produce precisely characterized responsivity to radiation in the UV-A (315nm-410nm), UV-B (280nm-315nm) and UV-C (240nm-280nm) wavelength bands. The filters also provide excellent rejection of interference from ambient visible and near infrared light sources.  

The AS7331 features an internal temperature sensor to support temperature compensation of measurement outputs. Digital measurements of radiant intensity are supplied in up to 24-bit resolution via a 16-bit I2C interface output.  

Low power consumption makes the AS7331 suitable for use in mobile or battery-powered products such as robotic floor cleaners. Operating current in active measurement mode is a typical 1.5mA at a 3.3V supply voltage, and the device draws a maximum current of just 970µA in stand-by mode.  

Housed in a 16-lead OLGA package, the AS7331 has a footprint of 3.65mm x 2.60mm, and is 1.09mm high. The AS7331 UV sensor is complemented by a wide range of UV LEDs from ams OSRAM, such as the new OSLON® UV 6060. This high-power UV-C LED offers market-leading wall-plug efficiency at highest germicidal effectiveness. 

The AS7331 UV sensor is available for sampling now. Mass production is expected to start in the first quarter 2023.  

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