Thermopile Sensors for IoT

mart and connected technologies are presently driving the astonishing growth of the Internet of Things (IoT). However, growth in these technologies is, in turn, a result of the tremendous development of various sensors. According to the Boston Consulting Group, by 2020, expect to spend US$ 265 billion for IoT technologies, services, and products. Much of this growth will owe its progress to that of sensors.

One can now find sensors almost everywhere, for instance, in smart retail, smart healthcare, and smart homes. Today, most people start their day with pressing a couple of apps while still in bed, thereby turning on the high-end coffee maker for the first-morning cup, or their night adjusting the climate control zoning system for keeping the bedroom in that ideal sleeping temperature.

As an example, a large health insurer in Australia is placing sensors throughout the house of elderly members for monitoring their health and preventing them from falling. They place sensors within refrigerators, medicine cabinets, bathrooms, and doorways. The sensors monitor movement by tracking the temperature within the home. Any break in routing such as a change in the temperature notifies the family immediately.

Viewers of professional golfing can see information on the heart rates of the players on their TV screens thanks to a special camera and sensors monitoring the faces of the players. This contactless vital sensing technique allows TV viewers to read the stress levels of the athletes as they play.

The past decade has seen a drastic drop in the prices of sensors as a result of the advancement of technology. This reduction has exponentially increased the use of sensors not only in civilian applications, but also in military, aerospace, and in collision avoidance systems in the automotive industry.

Advances in complex micro-electro-mechanical systems (MEMS) and thermopiles are improving uncooled IR sensor technology. This MEMS-based technology offers free-standing thermal isolation structures surrounding a printed thin-film IR absorber. This allows the collection of radiated power to determine the temperature of a remote object. Using semiconductor technology, it is now possible to add hundreds on thermocouples on several square millimeters of a thermopile sensor. Besides being small and reasonably priced, these thermopile array sensors are smart enough to be accurate with faster response time. It makes them ideal for building automation, people counting, security systems, medical instruments, and more.

For instance, the 8×8 thermopile array device is a sensor with 64-pixel IR sensors fitting within a surface mount package that can withstand reflow soldering. Apart from a silicon lens that collects the infrared energy, the package consists of a digital ASIC, a MEMS detector chip, and RF-shielded metal cover, and an I2C interface.

While operating, the thermopile array sensor has a 60-degree field of view for absorbing emitted thermal energy. The 64 sensing elements in the array individually convert the absorbed thermal energy to produce a proportional output signal. After amplification, an ADC converts these analog temperature signals to digital, while also referencing them against the ambient temperature value measured by a thermistor. A microprocessor collects the digital data and proceeds to map the temperature from individual thermopile elements into a thermal representation of the entire field of view.