Novel sensor is capable of detecting human presence without movement
There is no shortage of sensing technologies capable of detecting human movement.
Indeed, simple passive infra red detectors achieve this very successfully and are a common feature in many households. However, detectinh human presence in an area without movement is not so simple.
However, this is what is by Omron's D6T non-contact MEMS thermal sensor, a super-sensitive infrared temperature sensor that makes full use of Omron's proprietary MEMS sensing technology.
Unlike typical pyroelectric human presence sensors that rely on motion detection, the D6T thermal sensor is able to detect the presence of stationary humans by detecting body heat, and can therefore be used to switch off unnecessary lighting, air conditioning, etc automatically when people are not present (regardless of whether they move or not). As the D6T sensors are also able to monitor the temperature of a room, they can also be used to maintain optimal room temperature levels, instantly sense unusual changes in temperature, thereby detecting factory line stoppages, or discover areas of overheating for early prevention of fire outbreaks, etc.
Thermal sensors utilise the Seebeck effect in which thermoelectric force is generated due to the temperature difference at the contact points between two different kinds of metal. A thermopile is created by serially connecting thermocouples consisting of N+ poly Si , P+ poly Si, and Al. By creating hot junctions on highly heat-resistant dielectric membranes, and cold junctions on highly heat-conductive silicon, it is possible to achieve high-speed response and high-energy conversion efficiency (infrared rays, temperature, thermoelectric force).
D6Ts are created entirely from Omron's proprietary MEMS, ASIC, and other application-specific parts to ensure high sensitivity. They offer a particularly high signal-to-noise ratio, with a Noise-Equivalent Temperature Difference of 0.14 degrees Celsius.In addition, their low visual field crosstalk characteristics enable high-precision area temperature detection.
While standard thermal sensors are only able to measure temperature at one certain contact point, the D6T can measure the temperature of an entire area contactlessly. Signals generated by infrared rays are usually extremely weak, and high-sensitivity detection is therefore very difficult to achieve. However, Omron has developed and manufactured in-house every part of the new thermal sensor, from the MEMS sensors to ASICs (application-specific integrated circuits) and other application-specific parts, specifically with the aim of ensuring that the D6T is capable of highly sensitive detection.
The technology behind the D6T thermal sensors combines a MEMS micro-mirror structure for efficient IR radiation detection with a high-performance silicon lens to focus the infrared rays onto its thermopiles. Proprietary application-specific integrated circuits then make the necessary computations and convert sensor signals into digital I2C outputs. All components were developed in-house and are fabricated in Omron's own MEMS facilities. The result is high ±1.5°C accuracy with excellent noise immunity (measured as noise equivalent temperature difference) of 140mK.
In terms of applications, there is no shortage of possibilities. These range from aiding in the creation and development of new advanced energy-saving household appliances, through the enhancement of home and building energy management systems to a wide variety of factory automation applications. It could also be used in healthcare applications to see if a patient has left the bed.
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