Electricity + Control March 2019

TEMPERATURE MEASUREMENT

Non-contact infrared thermometers

IR detectors for consumer products have resulted in lower prices for these two im- portant components. Together with the in- creased demand for industrial IR thermom- eters, high volume production of standard sensors has resulted in greater manufac- turing efficiency for IR thermometer man- ufacturers. Second, IR sensors are becoming smaller in size. In the past, the measure- ment of low temperatures made it nec-

Temperature is one of the most common measurement parame- ters used for monitoring and control in process industries. In pro- duction as well as in quality control and maintenance, temperature can represent an important indicator of product quality or equip- ment condition. While thermocouples are among the most popular temperature measurement devices in industry, there has been a growing shift towards infrared, non-contact thermometers, also known as pyrom- eters.The reason for this can be attributed to the particular advantag- es of using infrared thermometers. These advantages include: • Fast response time (measured in milliseconds), the user re- ceives more information per time period • Capacity to measure objects that move, rotate or vibrate (such as items in production on a conveyor system or any moving object) • Capacity to measure high temperatures up to 3 000°C, where contact probes will not work or have a short lifetime • No mechanical damage or contamination of the surface (as required, for example, in production of food, pharmaceuticals, painted surfaces, soft plastics) • No influence of objects with high thermal-conductivity where object temperature would change if contacted (glass, wood, small or very thin objects). To ensure accurate and repeatable measurements certain condi- tions must be considered. • There has to be direct line of sight between the sensor and the object. • The optics of an infrared thermometer need to be protected against dust or condensation. • IR thermometers measure surface temperatures and the ability to emit thermal radiation depends on the kind of material and especially on the surface finish. Recently the infrared sensor market has seen two major trends emerging. First, IR thermometers are significantly lower in cost. The most expensive parts of an infrared thermometer are the lenses and detectors. New lens materials, technologies and mass production of

Non-contact infrared thermometers can measure temperatures up to 3 000°C in production processes.

essary to use fast lenses with relatively large diameters in order to capture enough emitted energy. Progress in detector technolo- gy and better detector performance, together with improved low noise analogue preamplifier techniques, have helped reduce the dimensions of the IR-sensing head dramatically. Because the new- er sensors have improved response characteristics they require less energy to achieve a usable signal. As a result, lenses can have smaller diameters. At R&C Instrumentation we have a range of infrared tempera- ture measuring devices. The Raytek range of portable units cover temperatures from -50°C to 3 000°C. Raytek was one of the first to introduce this technology, now a recognised industry standard. Fixed units from Raytek and Ircon are also well known industry standards. These scanners can be supplied as complete applica- tions packages with tried and tested software to suit various indus- trial applications. Continual innovation and new products like the Endurance and Thermalert series, designed by Raytek and Ircon working together, now combined as Fluke Process Instruments, will ensure a solu- tion for widely diverse temperature measurement and monitoring requirements. R&C Instrumentation’s applications engineers can assist and advise on the selection of infrared temperature measurement sys- tems for control and maintenance on process plants. Enquiries: R&C Instrumentation.Tel. +27 (0)11 608 1551, or email: info@randci.co.za

Electricity + Control

MARCH 2019

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