Extech-AN500-Anemometer-EXTECH-AN500-The-Extech-AN500-anemometer-s-new-sensor-technology-delivers-major-improvements-in-durability-&-automatic-temperature-compensation-ATC-for-accurate-in-duct-air-velocity-measurements-with-changing-air-temperatures-The-telescoping-probe-with-ruler-label-ensures-that-measurements-are-made-in-the-center-of-the-duct-even-if-out-of-reach-An-ergonomic-directional-handle-&-anti-rotation-sensor-confirms-that-probe-direction-&-airflow-direction-are-aligned