Observator Instruments OMC-150, Руководство пользователя

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Manual | OMC-150
Status: Final | Not confidential
Page 10 | 38
V2.13
See Appendix A: for a typical system layout. Note that the maximum length of the field cable, which runs
from the junction box (nearby the OMC-150 anemometer) through the Ex zone to the OMC-158-2
interface unit, is up to 1 km (depending on the cable quality).
3 Operation
3.1 General
The numbers in parenthesis refer to the item numbers on the assembly drawings in
3.2 Measurement of wind speed
The cup unit (6) is driven by the wind. There is an almost linear dependency between wind speed and
rotational velocity of the cup unit. The proportional factor is 1.68 meters per revolution. The cup unit is
connected to a shaft (12), which drives a metal slotted code cap (16). The transitions between the metal
partitions and the slots in this code cap generate pulses by means of an inductive proximity switch (10).
The code cap generates 8 pulses per revolution, so each pulse represents 0.21 meters
3.3 Measurement of wind direction
The stainless steel vane unit (4, 5) is driven by the wind. It turns until the counterweight (5) directs into the
wind direction. The position of the vane unit is transmitter through the shaft (12) and the coupling (17, 18)
to the dual wiper potentiometer (8). Figure 2 shows the typical output voltage in relation to the vane
position.
0 V
0 º 90 º 180 º 270 º 360 º
C
D
N E S W N
Figure 2 Output voltage on terminals C and D of the dual wiper potentiometer