Electricity + Control June 2018

round up CONTROL SYSTEMS + AUTOMATION

Using excess gain to choose a sensor

‘Moderately dirty’ environments can be found in heavy industry, food processing, or the automotive industry. For such envi- ronments, Banner recommends an excess gain 10 times more than what is minimally required. Very dirty – 50x EG Some environments like those found in foundries, mining operations, tile ovens, and outdoors are considered ‘very dirty.” This is because lenses and retroreflectors become heavily contaminated and are subject to minimal cleaning. There may be heavy fog, mist, dust, smoke, or oil film in the environ- ment. Banner recommends 50 times more excess gain in these types of environments. Enquiries: BrandonTopham. Email Brandon.topham@retautoma- tion.com

Excess gain is a measure of the minimum light energy needed for reliable sensor op- eration. The light signal that a sensor emits is factory-calibrated to a certain level of performance. However, contaminants in the sensing environment such as dirt, dust, smoke, and moisture, can cause signal at- tenuation. Excess gain may be seen as the extra sensing energy available to overcome this attenuation. Excess gain can be expressed as the fol- lowing formula. Excess gain = light energy falling on receiv- er element / sensor’s amplifier threshold. The threshold is the level of sensing energy required by the sensor's amplifier to cause the sensor's output to switch on or off. Important assumptions There are a few assumptions about using ex- cess gain to optimise the sensing function in an application. Use as high an excess gain setting as possible, without compromising target detection. In most sensing situations, excess gain correlates directly to sensing reliability. How to use excess gain to choose the proper sensor technology If the general conditions of a sensing area are known, the excess gain levels that fol- low may be used as guidelines for assuring

that the sensor’s light energy will not be entirely lost to attenuation. These guidelines include a safety factor for subtle sensing variables such as gradual sensor misalignment and small changes in the sensing environment. Clean air - 1.5x EG For a perfectly clean operating environment, an excess gain of 1.5x (50 % more energy than the minimum needed for operation) is suggested. Some environments that have ‘clean air’ include those found in the sem- iconductor or pharmaceutical industries. In these environments, no dirt builds up on the sensor lenses or retroreflectors. Slightly dirty - 5x EG An office or a clean factory might be char- acterised as a ‘slightly dirty’ environment. This means sensor lenses or retroreflec- tors may experience a slight build-up of dust, dirt, oil, or moisture. Lenses are cleaned on a regular schedule. In a ‘slightly dirty’ environment, the excess gain should be five times more than what is minimally

required for sensor operation. Moderately dirty – 10x EG

In a ‘moderately dirty’ environment, obvi- ous contamination can be seen on lenses or retroreflectors. These environments are also likely to have periodic wash-downs.

EcoStruxure for Industry

As the leader in powering and digitising industry, Schneider Electric is uniquely positioned to drive the digital transformation of today’s growing industrial automation markets and assist industrial customers in their conversions. Significant changes are funda- mentally accelerating this movement in the industrial space.

ment, and that figure is expected to grow by 25% year-on-year for the foreseeable future. This figure ties in with Accenture’s recent report, citing that at present, 64% of executives believe that a fail- ure to leverage digital will cause their companies to struggle for survival,” says Marc Ramsay, Vice President for the Industry Busi- ness Unit, Schneider Electric South Africa. Strengthening their commitment to digitising industry, Schnei- der Electric also unveiled EcoStruxure Machine Advisor during a presentation at Hannover Messe, 2018. EcoStruxure Machine Ad- visor now make it possible to track, monitor and fix machines in the field while reducing support costs by 30 to 50%. “Where managers struggle to track the history of the many ma- chines that fall under their scope of responsibility, or when parts need replacing, production is interrupted, and the downtimes are much too long. Maintenance technicians often spend far too much time attempting to locate different sets of documentation before they can begin productive work on fixing the machine. Schneider Electric’s recent breakthrough with this new technology is now di- rectly addressing these challenges by providing new ways of both gathering, centralising and displaying machine-generated data.” Enquiries: Zanelle Dalglish.Tel. +27 (0) 11 254 6400 or email zanelle.dalglish@schneider-electric.com

“With EcoStruxure for Industry, Schneider Electric offers a truly unified engineering approach that can be deployed across multi- ple industrial segments. Leveraging our unique partnership with AVEVA, we can offer an unmatched set of solutions covering all aspects of digital asset management from process simulation to design, construction and manufacturing operations management and optimisation,” Ramsay said. Schneider Electric’s EcoStruxure for Industry offers open, interop- erable, IoT-enabled system architecture and platform, where users benefit from enhanced value around safety, reliability, efficiency, sus- tainability, and connectivity. Leveraging all advancements in IoT, in- cluding mobility, sensing, cloud, analytics, and cyber security through connected products - Edge Control, Apps, Analytics and Services, EcoStruxure has been deployed in over 480,000 sites worldwide. “With the support of 20,000 system integrators and develop- ers, EcoStruxure currently has 1.6 million assets under manage-

14 Electricity + Control

JUNE 2018