Every Temperature Tells A Story - The growth of contactless temperature measurement on the IoT
- Published: Tuesday, 11 February 2020 08:19
Temperature is a parameter that can tell a story. Abnormal temperatures are often the first sign of wear and tear, electrical faults and other issues. They can warn of a potential fire before it actually starts.
Temperature measurements can detect the presence or absence of people, or to confirm that a system is operational. That’s all in addition to the direct role of temperature measurement in controlling ovens and heaters.
Very often, it isn’t possible to measure temperature directly, by attaching a probe. This is where contactless temperature sensors are useful. From the detection of abnormal temperatures in industrial equipment on the production line to monitoring of food and other temperatures in the kitchen, contactless sensors like the MEMS-based Omron D6T make a valuable contribution to safety – identifying potential problems before they become major hazards. This can not only save lives but also costs, allowing preventative maintenance to be undertaken in a timely manner.
Advantages of integrated signal processing
Omron D6T MEMS thermal sensors are based on an IR sensor which measures the surface temperature of objects without touching them using a thermopile element that absorbs radiated energy from the target object. Incorporating a state-of-the-art MEMS thermopile, custom designed sensor ASIC and signal processing microprocessor and algorithm into tiny package, the D6T is believed to offer the highest signal-to-noise ratio (SNR) in the industry. This ensure clear, reliable measurements that can readily be interpreted by the system.
A key advantage of the integrated signal processing microprocessor is the fully linear output (figure 1 - left). By pre-processing the signal on the module, the D6T converts the sensor signal to a digital temperature output giving a straightforward interface to a microcontroller, simplifying system integrator’s task. Alternative devices don’t provide a temperature output, so the designer needs to implement a signal processing algorithm to convert the output to temperature.
Despite the inclusion of the microprocessor, Omron has achieved a space saving design for the D6T, at only 14 x 8 x 8.93 mm for the largest 32 x 32 element version, making it exceptionally well suited to temperature detection in a wide range of Internet-of-Things and other embedded applications.
Selecting a contactless sensor
In addition to the temperature range the key parameter in selecting a contactless sensor is the field of view. Often, manufacturers create a wider field of view by combining multiple individual sensor elements into a module. A wide field of view isn’t always desirable: sometimes a targeted measurement of a specific object or area is required.
For example, the single element Omron D6T-1A-02 has a viewing angle of just 26.5° x 26.5° translating to an area of 47x47cm at a distance of 1m, giving a highly directional characteristic. By contrast, the latest addition to the Omron range, the 32 x 32 element D6T-32L-01A (figure 2) can view across 90.0° by 90.0°. At 1m, this translates to an area of 200 x 200cm, and this sensor is able to encompass a wide area such as a whole room from a single point. Applications where a more restricted field of view is needed can be fulfilled by the 1x8 D6T-8L-09H and the 4x4 D6T-44L-06H, offering 54.5° x 5.5° (103 cm x 10cm) and 44.2° by 45.7° (81cm x 84cm) respectively.
Contactless sensors can be applied to a whole range of different environments. Depending on the requirement, temperature bands of 5 to 45ºC, -40 to +80°C, 0 to 200ºC can be specified.
Temperature measurement is a growing issue more and more systems are connected to the Internet of Things, and expected to operate remotely. Contactless temperature monitoring devices are growing in sophistication as the technology develops. With a wide range of field of view characteristics and a choice of thermal profile, there is now a solution for a great many industrial monitoring applications. Devices with direct, linear temperature outputs make system integration particularly straightforward. This is definitely the technology of the future for temperature monitoring on the IoT.
By: Gabriele Fulco, European Product Marketing Manager, Omron Electronic Components