According to Johnsy Varghese, the marketing manager for wireless at ams, investigating ways that sensors can add value to new applications is a continuous process for his company. In the case of the Product of Year Award-wining AS3935 Franklin Lightning Sensor, he says, “We saw this opportunity as a way to innovate — with a new sensor, in an untapped category, that could be used in a meaningful way by consumers.”
Over many years, weather forecasting has undergone a massive transformation: from the days when the farmer's sciatica “acting up” was the predominant indicator, to an approach in which sensor readings from around the globe are amassed by teams of scientists to determine current and likely future conditions. And while many people often get an early morning forecast, weather can change rapidly without notice. Yet scientific lightning prediction capability is an area that is still little known to the public, making people depend on “natural instincts” like those of the farmer, which usually occur when it's already too late to avoid danger. With the Franklin Lightning Sensor, the intention is to help average citizens be constantly aware of the meteorological environment, even while they pursue outdoor activities far from TVs and cell-phone towers.
It was in late 2007, early 2008 when some top ams project leaders began to put together specification for the product. A digital designer worked on top-level mixed-signal simulations, along with a top analog and software designer who had extensive knowledge of systems software and datalogger systems. Based on that work, ams green-lighted the project in 2008.
The actual design wasn't simple. The device had to be extremely reliable and able to discern real lightning from man-made disturbers; if the device gave false indications, it would be “The Boy Who Cried Wolf,” whose warnings would be ignored at the worst possible time. The sensor would also have to be highly integrated, small, and need little power in order to be universally available. To deliver those capabilities, ams would have to develop a highly sensitive low-power receiver, unique lightning-sense capability, automatic antenna tuning, and a proprietary algorithm that enables true lightning detection and distance estimation, isolating disturbers and noise in the measurement environment.
Varghese remembers that “these requirements themselves challenged us for some time.” After reviewing multiple approaches and trials, ams designers decided to do some preprocessing in analog, using a low-noise amplifier (LNA) followed by specialized detection circuitry. This unique detection circuitry was used to discriminate between lightning and several kinds of disturbers. Another challenge was how to post-process all the data available. The decision was made to integrate a custom controller, instead of using an external processor. This controller allowed use of a specialized algorithm to minimize disturbers while keeping overall power low and the overall system small.
Along with a wealth of meteorological data, the ams product team (which included the design team, process engineering, fabrication engineers, and quality and test engineers) was able to use the unique high-performance capabilities of the company's in-house fab facility. The analog/software designer was also involved in multiple post-design tasks to bring the device into production, as the company also engaged with a university in Florida that is a leading lightning-research. With their help, ams conducted extensive field trials in Florida, Austria, and Finland. The university compared the Franklin sensor's data with that of the NLDN (the National Lightning Detection Network, which most weather agencies rely on for data) and found good correlations.
Including field trials and validation, it took about four years of intensive effort to bring the product to market in 2012. Based on the large number of customers' sample requests and development boards, initial market interest was very high. As with any new technology, especially those that are ground-breaking, the time to market for end products can be somewhat longer than standard-technology products. Many customers are actually testing the products independently: Varghese says, “Each customer wants to do some validating on their own before going to the market and, since storms cannot not be commanded to appear on-demand, it takes a little time and 'coordination' with Mother Nature.” To date, customer feedback has been very positive; in their trials and evaluations, the product has detected storms and provided distance estimations to the head of the storm, just as it was designed to do.
Based on this response, ams plans to broaden its lightning-sensor product category in the near future, and is looking at ways to expand the sensing capabilities of the Franklin Lightning Sensor.
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