Operator`s manual
SECTION 8. PROCESSING AND PROGRAM CONTROL EXAMPLES
8-7
02: 60 minute interval
03: 10 Set high Flag 0 (output)
11: P69 Wind Vector
01: 1 Rep
02: 180 Samples per sub-interval
03: 00 US, DV, SD (Polar Sensor)
04: 1 Wind Speed/East Loc WS
05: 2 Wind Direction/North Loc
0-360 WD
12: P71 Average
01: 2 Reps
02: 3 Loc Ta
13: P End Table 1
8.6 CONVERTING 0-360 WIND
DIRECTION OUTPUT TO 0-540 FOR
STRIP CHART
If 0-360 degree wind direction is output to a strip
chart, the discontinuity at 0/360 will cause the
pen to jump back and forth full scale when the
winds are varying from the north. In the days of
strip charts this was solved with a 0-540 degree
pot on the wind vane (direction changes from
540 to 180 and from 0 to 360 so the pen only
jumps once when the wind is out of the north or
south).
When faced with the necessity of strip chart
output (see previous example), the following
algorithm can be used to change a 0-360 degree
input to 0-540. (If you have a 0-540 pot, it can
be used with the 21X since the Wind Vector
Instruction, 69, will work with this output.)
To change 0-360 degrees to the 0-540 degrees,
360 degrees must sometimes be added to the
reading when it is in the range of 0 to 180. The
following algorithm does this by assuming that if
the previous reading was less than 270, the
vane has shifted through 180 degrees and does
not need to be altered. If the previous 0-540
reading was greater than 270, 360 degrees is
added.
This example is written as a subroutine which is
used by the previous example to output an
analog voltage to a strip chart.
Input Location Labels:
1:WS
2:0-360 WD
3:Ta
4:SR
5:WS output
6:0-540 out
7:Ta output
8:SR output
10:0-540 WD
* 3 Table 3 Subroutines
01: P85 Beginning of Subroutine
01: 1 Subroutine Number
02: P89 If X<=>F
01: 10 X Loc 0-540 WD
02: 3 >=
03: 270 F
04: 30 Then Do
03: P86 Do
01: 11 Set high Flag 1
04: P94 Else
05: P86 Do
01: 21 Set low Flag 1
06: P95 End
07: P31 Z=X
01: 2 X Loc 0-360 WD
02: 10 Z Loc [:0-540 WD]
08: P89 If X<=>F
01: 10 X Loc 0-540 WD
02: 4 <
03: 180 F
04: 30 Then Do
09: P91 If Flag
01: 11 1 is set
02: 30 Then Do
10: P34 Z=X+F
01: 10 X Loc 0-540 WD
02: 360 F
03: 10 Z Loc [:0-540 WD]
11: P31 Z=X
01: 10 X Loc 0-540 WD
02: 6 Z Loc [:0-540 out]
12: P 95 End
13: P 95 End