Campbell Scientific CR10 CR10 Measurement and Control - Page 118

SECTION

8.

PROCESSING

AND

PROGRAM

CONTROL EXAMPLES

09:

P

01:

4

02:

30

03:

5

10:

P92

01:

0

02:

60

03:

10

11:

P69

01:

1

02:

180

03:

00

04:

1

05:

2

12:

P71

01:

2

A2:

3

103SDM-AO4

Reps

Address

Loc

WS

output

lf

time

is

minutes into

a

minute interval

Set high Flag

0

(output)

Wind

Vector

Rep

Samples per sub-interval

Polar

Sensor/(S

,D1,

SD1)

Wind Speed/East

Loc WS

Wind

Direction/North Loc

0-360

wD

Average

Reps

Loc

Ta

13:

P

End

Table

1

8.7

CONVERTING

0.360

WIND

DIRECTION OUTPUT

TO 0-540

FOR

STRIP

CHART

lf 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.

(lf

you

have

a

0-540

pot,

it

can be

used with

the

CR10 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

27O,

the vane

has shifted

through

180 degrees and

does

not

need

to

be

altered.

lf

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.

>=

F

Then

Do

*3

01:

P85

01:

1

02:

P89

01:

10

02:

3

03:

270

O4:

30

03:

P86

01:

11

04:

P94

Input Location Labels:

2:0-360 WD

6:0-540 out

10:0-540 WD

05:

P86

01:

21

06:

P95

07:

P31

01:

2

O2:

10

08:

01:

o2:

03:

o4:

09:

01:

02:

10:

01:

02:

03:

11:

01:

02:

Table 3 Subroutines

Beginning of Subroutine

Subroutine Number

lf X<=>F

X Loc 0-540 WD

Do

Set high Flag

1

Else

Do

Set low Flag

1

End

Z=X

X

Loc 0-360 WD

Z

Loc

[:0-540

WD]

lf X<=>F

X Loc 0-540

WD

F

Then

Do

lf

Flag/Port

Do

if

flag

1

is high

Then

Do

Z=X+F

X

Loc 0-540 WD

F

Z

Loc

[:0-540

WD]

Z=X

X

Loc 0-540 WD

Z Loc

[:0-540

out]

End

End

Table

3

End

End

P89

10

4

180

30

P91

11

30

P34

10

360

10

P31

10

6

P95

P9s

P95

P

13:

't4:

15:

8-8

Campbell Scientific CR10 CR10 Measurement and Control - Page 118

To 0-540, Chart

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