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 become a new norm for the foreseeable future, there are opportunities for sensing technologies to provide extra protection and greater convenience in the environment around us. David Pearson, Technical Director at Anglia Components, introduces a portfolio of Omron solutions that draw on the company’s expertise in presence, proximity, temperature and touch sensing. In addition to typical applications such as security and energy management, we will look at how one of Omron’s sensor ranges are ideal for contactless measurement of raised body temperatures; a coronavirus symptom that can be easily detected by an automated system.
Many regions across the globe have introduced legislation to try and minimise social contact between people and thus slow down the spread of the virus. These have ranged from more or less complete lockdown, requiring people to stay in their homes as much as possible, to recent relaxations aimed at restoring limited social interaction albeit from a distance.
Behavioural protocols everywhere are changing, from mandatory face coverings on public transport to use of shared facilities such as office or public washrooms. Businesses are becoming dependent on contactless point-of-sale transactions and Internet shopping for their survival, with new rules for the delivery staff responsible for fulfilling orders placed safely online.
The World Health Organisation (WHO) has published interim guidance regarding transmission of the COVID-19 virus via contaminated environmental surfaces advising cleaning to help remove or significantly reduce virus pathogens as an essential first step in any disinfection process. Another method of effective control can be to reduce physical contact with these potentially contaminated surfaces.
Photo sensors are already widely used to automate equipment such as door openers, hand sanitiser dispensers, bathroom taps and toilet flushers. Contactless operation in such high-traffic applications is effective in reducing the spread of germs.
ne challenge with many photo sensors available on the market is that they can be affected by objects in the background of the field of view, intense ambient light, and movement. Omron’s B5W photo sensors get around these challenges by using a Light Convergent Reflective (LCR) sensing method making them inherently less susceptible to variations, allowing the intended object to be sensed reliably and accurately. They have a wide sensing range to allow object shifting and also have a longer detection distance. The sensor’s convergent light beam can be accurately set to trigger on the presence of an object within a tightly specified target area, ignoring any objects in the background or foreground, and are particularly well suited to detecting challenging objects such as those that are reflective, transparent, or diffuse.
Keep it Clean
In other applications such as lift controls or vending machines where contactless operation may not be viable, touch sensors provide a reliable alternative to traditional mechanical switches currently used. Post-coronavirus, the ability to clean a touch sensor more easily than an array of switches has become an attractive option.
Capacitive touch sensors usually require careful design and integration, also complex setting up is often needed to ensure that they work reliably in the application. Omron W7ED capacitive touch sensors have been designed to remove the need for this complex design and setting up requirement, the sensor can simply be fastened to the touch electrode in the system with a screw. Once connected the sensor can reliably detect the capacitance change caused by the presence of a finger without the need to design or incorporate a control PCB or to perform complex sensitivity and calibration adjustments. These self-contained sensors combine the simplicity of a mechanical switch with the advantages of touch control and enable designers to create more aesthetically pleasing products. They can be used with wet hands or when wearing latex gloves as personal protective equipment, permitting additional safety as well as making control surfaces much easier to clean.
As we endeavour to return back to more normal ways of interacting with visitors to our homes or offices – whether delivery drivers or other contacts such as family members, work colleagues, business associates - a fast, effective and, above all, inoffensive way of checking the health of those we encounter could be extremely helpful.
One of the most obvious signs of infection is a raised body temperature. Being able to detect this in a visitor on arrival can protect occupants and also help warn the individual, who may not know that they could be infected.
Omron’s D6T thermal infrared sensors could provide a convenient solution. These accurate non-contact temperature sensors 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 well suited to embedded applications and relieves key signal-processing workloads from the system host processor.
D6T sensors can be added to an access-control system, for example, to automatically check the temperature of a visitor on arrival (figure 1).
Figure 1. Accurate non-contact temperature measurement for access control and protection.
Sensor Family for Versatile Monitoring
The family of D6T far-infrared sensors brings the advantages of continuous non-contact temperature measurement to a variety of applications, particularly accurate occupancy and proximity sensing.
The D6T family offers sensors in a variety of sizes from single-pixel sensors to devices with 4x4 and 32x32 pixels (see table 1), and with different viewing angles, to address numerous applications in building automation, energy management, security, industrial, predictive maintenance and safety. The 4x4 and 32x32 pixel array sensors are well suited to body-temperature sensing applications.
Table 1. The D6T family includes sensors from single-pixel to multi-pixel devices.
Accurate Body-Temperature Measurement
The typical accuracy of D6T sensors, as supplied, is ±1.5°C. To use these devices in a precision body-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 4). 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.
Figure 4. Calibrating with reference temperatures.
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 this formula:
Thanks to the integrated signal-processing ASIC, D6T sensors output the digital temperature value via an I2C interface that the host system can read directly. The sensor 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 temperature checking.
Access Control and More
Anglia can supply the full range of Omron B5W light convergent reflective photo sensors, W7ED capacitive touch sensors, and D6T non-contact temperature sensors for future generations of automated devices designed to further improve safety and help prevent the spread of disease. Samples and evaluation tools are available free of charge to registered account customers within EZYsample. Anglia field application engineers are trained and ready to help you select the right sensors for your needs and take full advantage of their superior features in your next project.
Visit www.anglia-live.com or scan the QR code to discover more about these sensors and other Omron products available from Anglia.