Campbell 21X Manual do Operador descarregar pdf (Página 90)

SECTION

8. PROCESSING

AND

PROGRAM CONTROL EXAMPLES

Beginning of Loop

Delay

Loop Count

Do

Set

high Flag

0

(output)

Resolution

High Resolution

Sample

Rep

Loc

End

Do

Set high

Flag

1

End

Table

1

Mode 10 Memory

Allocation

lnput Locations

lntermediate Locations

8.8.2 EXAMPLE

WITH

BIN AVERAGING

The 21X was used to

generate

data simulating

wave

data from an ocean

buoy

with four

superimposed sine wave

signals, 0.1, 0.125,

0.14, and O.2Hz.

The

2048

generated

samples

simulate a sampling

rate of 0.5 Hz or a2.O

second scan

rate.

Figure

8.8-3 shows a

plot

of

part

of the simulated

signal.

A FFT with 8

bin

averaging was

performed

on the data. A

multiplier of 0.1

was used to

keep

the

FFT

results

smaller than

the

+6999 upper limit

of

low

resolution

Final Storage.

The results

of the

FFT

are shown Table 8.8-4

and are illustrated in

Figure

8.8-4.

In

the

example

program,

a multiplier of 0.1 is

used

in the

FFT

lnstruction.

By

reducing the

FFT

results by

a

factor of

10,

the

Low

Resolution

output format

can be used, thus

maximizing

the Final

Storage capacity. A

Low

Resolution

data

point

requires 2 bytes of Final

Storage

memory, while

a High Resolution data

point

requires

4

bytes.

When memory is

a

limiting

factor,

the data

should be scaled to be

less

than

6999,

so the

Low Resolution

format

can be

used.

SINULATED

OCEAN

WAVE BUOY

DATA

feo/fL

.t/tr. .rb/?. .\./6,

.2/.

o 6

12

16 2. JO

)6

42 4! 5. 60 66

72

76

O.

90

96

to2r6ll'

Iffi N 5ECAOs

FIGURE 8.8-3.

Simulated

Ocean Buoy

Wave

Data

SII1ULATED

OCEAN

WAVE BUOY

FFT

RESULTS

areo/

Et

.r

/

1 r.

-123/9.

.1

1/6, .2/.

o-@r95 0.0)12 0-ru.5

0.697

0.rro95

0.t.t2 0.17t.5 0.267

0 2595

trr

ftwrcrEs

(o-oot95-o.2.7c5

tu)

FIGURE 8.8-4.

Simulated

Ocean Buoy

FFT

Results

13: P87

01: 0

Q2:

512

14:

P86

01:

10

15: P78

01:

1

16: P7O

01: 1

O2: 1-

17: P95

18: PBo

01: 11

19:

,t

'A

01:1030

02: 260

o.9

o.a

0.7

o.6

o.5

o-a

o.J

o.2

o.r

&14

1 2 ... 85 86 87 88 89 90 91 92 93 94 95 ... 190 191

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