Winds greater than 155 mph. Storm surge generally runs greater than 18 feet above normal. Complete roof failure on many residential and industrial buildings. Some complete building failures with small utility buildings blown over or away. All shrubs, trees and signs blown down. COMPLETE DESTRUCTION of mobile homes. Extreme damage to doors and windows. Low-lying escape routes cut by rising water 3-5 hours before the arrival of the hurricane's center. Major damage to all lower floors of all structures located below 15 feet above sea level and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5-10 miles of the coastline maybe required. Minimum central pressure (920 mb or lower)
Others, however, have shied away from this robustly realist approach to categories, generally on grounds of skepticism about our ability to discern intrinsic divisions in ‘reality itself’, and have instead treated the project of categories as a matter of laying out the highest categories governing our conceptual scheme. This shift in approach to what Carr (1987, 6) calls “categorial conceptualism” was made famous by Immanuel Kant. While Kant famously denied that we have access to intrinsic divisions (if any) of the thing in itself that lies behind appearances or phenomena, he held that we can discover the essential categories that govern human understanding, which are the basis for any possible cognition of phenomena. Thus, as H. J. Paton puts it, for Kant “We can have a priori knowledge by means of the categories, only if the categories are due to the nature of the mind and are imposed by the mind on the objects which it knows” (1936, 258).
What Do All These IEC Definitions Mean for You?
Knowing the IEC definitions, you can understand what your present measurement instruments can do and what you need to buy in the future.
For example, a 250 V RMS Category I DMM is not rated to measure standard wall socket voltages. The DMM is not designed to withstand the transient voltages on the power line. However, a Category II 500 V RMS DMM, such as the NI PXIe-4081 7½-digit DMM, is designed for measuring wall socket voltages. It contains the extra insulation necessary to withstand wall socket transients.
When measuring high voltages, safety is of great concern. When using your existing equipment or buying new equipment, pay attention to more than just the working voltage rating. Make sure your equipment meets the UL, CE, or IEC standards you need. That way you'll be assured that the high voltage goes into your measurement circuit instead of you!