Campbell 21X Manual do Operador descarregar pdf (Página 84)

SECTION

8. PROCESSING

AND PROGRAM

CONTROL

EXAMPLES

15:

P

End

Table

3

8.7

COVARIANCE

CORRELATION

PROGRAMMING

EXAMPLE

The'example

is

a 2 level meteorological

tower

with 5 sensors

at

each level. The

three

components

of the wind are measured

using

prop

anemometers.

Two

thermocouples

(TC)

are

used

to measure

ambient

and

wet-bulb

temperatures and

calculate

water

vapor

pressure

on-line.

All

sensors

are

scanned

once

per

second

(1

Hz) and

a

5 minute

averaging

period

with

a

30 minute Output Interval

is

specified.

The

example optimizes

the input

measurement

sequence for

speed

and shows

the

instructions

necessary

to

provide

calibrated

inputs,

properly

ordered to

produce

the desired

outputs

from

the

Covariance Correlation

(CV/CR)

Instruction.

Table 8.7-1

groups

the

sensors according

to measurement

type and

gives

the

21X multiplier and

offset.

DESCRIPTION

Horiz.

Wind

Horiz. Wind

Vert. Wind

Air Temp.

SENSOR

prop

prop

prop

TC

TC

derived

Wet-bulb Temp.

Vap. Pressure

The

props

can all

be measured as single-ended

voltages, but the verticalwind

prop

calibration

differs from the

U and V

prop

calibration. The

fastest input sequence

is to measure both

(6 props)

with a single instruction

using the

U

and V calibration and

correct the

W

measurements with

the Fixed

Multiply,

Instruction

37.

The

type E thermocouples

are measured on

most

sensitive

input

range, 5mV,

accommodating a

t80oO

range between the

measurement and 21X

reference

junction.

The

resolution is

(.33pV/(60pVPC)

or

about

0.006oC

Measuring

absolute temperature with TCs

requires

a

reference

junction

temperature

measurement. This is measured with

17.

The

specified outputs determine the input

order

required

by the CV/CR Instruction. Table 8.7-2

lists

the desired outputs from

the

two levels

along with

the Input

Storage locations tor the

processed

results.

14:

TABLE

8.7-1.

Example

Sensor

Description

and 21X

Multiplier

and Offset

SYMBOL

0.0

0.0

0.0

0.0

0.0

U

v

w

Ta

Tw

e

CALIB

18m/sA/

18m/slV

*v:*

MEAS TYPE

s.E.v.

s.E.v.

s.E.v.

TC DIFF.

TC DIFF.

MULT

.018m/s/mV

.018

.o22

1.OoC

1.0oC

8-8

1 2 ... 79 80 81 82 83 84 85 86 87 88 89 ... 190 191

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