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The COVID-19 pandemic remains at the forefront of people’s minds and the world is looking to utilise helpful technologies to come up with solutions. With social distancing set to be with us for the foreseeable future, the need for sensing technologies to provide extra protection and greater convenience in the environment around us has never been greater.

Omron has risen to the challenge with their innovative Thermal Infrared sensors, the D6T family, these sensors offer accurate non-contact temperature measurement and feature a silicon lens and MEMS thermopile to detect far-infrared radiation emitted from the surface of the face or body. A signal-processing ASIC integrated in the same package converts the sensor output to a digital temperature reading and ensures a high signal to noise ratio (SNR). The result is a compact device that is very well suited to embedded applications and relieves key signal-processing workloads from the system host processor.

The D6T sensors are available in 1x1, 1x8, 4x4 and 32x32 pixels and a variety of viewing angles to suit a wide range of applications. For example the 1x1 pixel sensors are very well suited to predictive maintenance and safety systems in industrial applications such as monitoring bearing temperatures on motors as an early warning sign of possible failure. Other typical uses include building automation and energy management where the sensors can be deployed for occupancy detection and thus control heating, lighting and security systems accordingly.

Unlike traditional PIR sensors that rely on movement to detect presence, the D6T sensors are able to detect presence even when the person is stationary, this enables them to be used in smart building management applications as intelligent replacements to traditional PIR sensors but also in new applications including healthcare e.g. to monitor occupancy of hospital beds and alert carers if a patient needs assistance whilst at the same time maintaining the patients privacy.

A key applications that has emerged where the D6T sensors are particularly suited is accurate body surface temperature measurement, a high temperature is recognised as one of the key indicator symptoms of COVID-19 therefore the ability to accurately and contactless measure a person’s surface body temperature is important for access control and protection. The D6T 4x4 and 32x32 pixel array sensors are well suited to this application, Omron’s vast experience in temperature measurement means they have the know-how to get the required accuracy for this application.

Click below for an overview of how D6T can provide accurate temperature measurement

Achieving Accurate Body-Temperature Measurement

The typical accuracy of D6T sensors, as supplied, is ±1.5°C. To use these devices in a precision body surface temperature monitoring context such as coronavirus infection checking an accuracy of ±0.2°C is ideally required, this means additional custom calibration is recommended for increased accuracy. An effective way to calibrate the sensor is to start by setting both the upper target temp (y0) and the lower target temp (y1) to cover a suitable range. For an access-control system, designed to assess the surface temperature of a human face, a typical range could be from about 32°C to 38°C. To calculate a correction factor and thus ensure accurate temperature measurement with D6T sensors, a calibration source such as a blackbody furnace can be used (figure 1). The source is set first to the lower limit temperature (let’s call it y0) and measured with the D6T. We recommend recording, say, 10 measurements to get an average sensor output reading (x0), making sure first to allow about 15 minutes for the system to stabilise after powering on. The source is then set to the upper maximum temperature (y1), and the average of a second set of sensor readings (x1) taken in the same way as before.

Fig.1

Using the reference source settings and recorded temperature measurements, the calibrated target object temperature, y, for any given sensor output reading, x, can be calculated using the following formula:

Thanks to the integrated signal-processing ASIC, the Omron D6T sensors output the digital temperature value via an I2C interface that the host system can read directly. The sensor also comes mounted on a PCB with terminations provided, allowing easy integration into the end application.

Omron have many years of experience in contactless temperature measurement and can provide guidance and advice to designers on how to get the accuracy of the D6T down to the ±0.2°C required for effective human body surface temperature checking.

Anglia are offering customers FREE samples of the D6T sensors from Omron, please fill in the form below to register your interest now.