SKY DEVELOPMENT: A LOOK BEHIND THE SCENES
Wind. The ultrasonic anemometer technology employed by SKY to measure wind speed & direction has been around for years. It’s an ingenious idea: transmit a sonic signal between two sensors, record the time-of-flight each way, and the difference is the speed of the air moving between the two. However, implementing it in such a low-cost, low-power package as ours, is where it gets really tricky. Our engineers have developed incredibly clever algorithms that enable SKY to report wind speed very accurately. Nevertheless, to maintain that accuracy, there are several critical geometries that must be held to a very high tolerance. The electronic components must also be precisely made, and everything must be assembled following strict QA procedures in order to maintain consistency from device to device.
Rain. Key to our promise of a low-cost, maintenance-free, no-moving-parts weather station is our haptic rain sensor design. Like the sonic, it has never been done in such a low-cost product. With our patent-pending design, calibration against precision tipping buckets in actual rain is pretty straight forward, and device-to-device variability is less of an issue. The trick here is developing a simple “dry calibration” step that can be done quickly and repeatedly on the assembly line. We created a “rain test jig” that produces a statistically uniform and consistent pattern of “rain.” And we’ve experimented with things like beany baby beans, BB’s, gum balls, breakfast cereal, and about a dozen other candidates in the hunt for “best rain drop surrogate.” Israeli couscous was the winner in off-the-shelf products. From that point, the task was to identify a durable, synthetic material with similar properties - something that won’t wear out after repeated test cycles through the calibrator. (see video)
Sun. Compared to wind & rain, development of the sun sensor (which reports UV, solar radiation and brightness), is a much simpler task. Nevertheless, the same device-to-device tolerances are critical to maintaining accuracy on a production scale. This process has gone through several design iterations with rigorous testing both indoors under a standard light source and outdoors in natural sunlight. In testing to date, we are seeing very good correlation between SKY and expensive calibrated pyranometers.