OCR Text |
Show deflected slightly by a solenoid, so that each line has two positions on the charts, depending on whether or not the solenoid is energized ( See Figure 2). The one- mile anemometer contact can be wired to operate a solenoid ( two conductors required). Several anemometers can be recorded simultaneously. Contact arcing causes a serious maintenance problem unless the circuit in Figure 3 is used. This solid- state relay completely eliminates inductive surge at the anemometer contacts, as well as the effects of losses introduced by line resistance. By thus reducing the required size of cable conductors, this circuit can lead to large savings on long wi re 1ines. The operations recorder can also record wind direction. A contact wind vane ( A26) is used which closes any one of eight electrical contacts, depending on which cardinal direction of the compass the vane is indicating. Each contact is wired to a separate pen solenoid of the recorder. Figure 2 shows the character of the record obtained. A fully- operational direction record requires nine conductors in the telemetry cable-- eight for the position contacts and one common return. This common return may also be used for one of the anemometer conductors, so a total of 10 conductors is required for speed and direction ( 12 if the circuit of Figure 3 is used with the anemometer). The number of conductors required can be reduced by sacrificing recorded wind directions, one conductor to a direction. The heavy- duty operations recorder ( A28a) demands considerable power. Each 6- volt solenoid draws approximately 0.25 ampere when energized. If wind direction is being recorded, at least one solenoid is always energized. An adequate DC power supply must be provided. A storage battery and charger ( A39) connected to line power are desirable, for this permits a number of hours operation from the battery in case of power line failure. The charger described will operate the system without the battery. The electrical contacts in the wind vane ( A26) are much heavier than in the anemometer and normally can sustain the effects of contact arcing with less damage. The use of a capacitor or diode arc suppressor across the wind vane contacts will keep this problem to a minimum, although sound maintenance procedures cannot be ignored. It is possible to use the circuit of Figure 3, but a separate complete circuit is required for each contact. The combination of contact anemometer/ wind vane and spring-driven operations recorder has been proven reliable by many years of use and provides a satisfactory wind record for snow safety operations. The digital record it provides can be easily counted for transcription to the wall charts or other record forms. It also eliminates all calibration problems, for the calibration is fixed in the design of the anemometer. But the wind run record 8 |