| OCR Text |
Show must be sturdy enough to withstand high winds and must not interfere with flow of air around the anemometer cups. Details of construction are obvious from Figure 15. Where riming is a frequent cause of anemometer damage and no electric power is available, it may be necessary to resort to a different and more rugged anemometer. There is one model of contact- type anemometer ( A24b) wtvich has proven capable of surviving extremely severe rime and high winds. Use of this sensor of course requires a digital rather than an analog wind system. Conversion of an existing analog system to a digital anemometer is possible. Contact the Alta Avalanche Study Center for details if this conversion becomes necessary. Wind vanes appear to be much less susceptible to rime damage than anemometers. They simply freeze up and quit functioning until the rime is removed. Lightni ng Lightning is an ever- present danger to mountain instrument installations. It is more apt to be a problem in summer and fall than in winter, but even then it may sometimes damage equipment. The proper protection for operating equipment is thorough grounding of all tower, cable shields and instruments, plus installation of lightning arrestors at cable terminals. Sensitive instruments such as meters and recorders should be protected with fuses appropriate to the current- carrying capacity of the circuits involved. It is important that fuses installed for lightning protection should be at the actual meter or recorder terminals ( in- line fuses). If such fuses are located inside junction boxes or electronic chassis, it is still possible for electrical surges to by- pass them and enter the sensitive equipment. The best protection during non- operating periods in summer is to remove the sensors ( anemometer, thermistors, etc.) from the field and store them. Cables should be disconnected at junction boxes and meters or recorders disconnected from their signal inputs. A few moments spent each spring disconnecting wires and each fall reconnecting them can save a large amount of trouble and expense. It takes just one lightning strike, or even a ground current surge, to ruin a lot of expensive equipment. 48 |
