Campbell Scientific CR10 CR10 Measurement and Control - Page 159

average of all

the

readings in

locations

1-10

since

the

previous

output.

Because

the

lntermediate

locations are zeroed each time an

output occurs,

the

next nine values

will

be

the

current

values

(samples at the

time

of output) of

locations 2-10.

Loops

can be

nested.

lndexed locations within

nested loops

are

indexed to

the

inner most loop

that

they

are

within.

The

maximum nesting

level

in

the

CR10 is

9

deep.

This applies

to

lf

Then/Else

comparisons

and Loops or any

combination

thereof.

An

lf Then/Else

comparison

which

uses

the

Else Instruction

(94)

counts as being nested 2 deep.

PARAM.

DATA

NUMBER

TYPE

DESCRIPTION

01:

4

Delay

02:

4

lteration

count

The

following example

involves

the

use

of

the

Loop Instruction, without a delay,

to

perform a

block data transformation.

The

user

wants

'l

hour averages

of

the

vapor

pressure calculated from the wet- and dry-bulb

temperatures

of

5 psychrometers.

One

pressure

transducer measurement

is

also

available

for

use

in

the

vapor

pressure

calculation.

1.

The input

locations are assigned as follows:

a)

pressure

Location

10

b)

dry-bulb temperatures

Location

1

1-15

c)

wet-bulbtemperatures

Location 16-20

d)

calculated

vapor

pressure

Location

21-25

(Vapor

pressure

is

written over

the

wet-bulb temperatures.)

2.

The

program

flow

is as follows:

a)

Enter

the

Loop

lnstruction

(#87) with

DelaY=O

and iteration count=5.

b)

Calculate the

vapor

pressure with

Instruction

57

using

a

normal location

entry

of

10

for atmospheric

pressure

and

Indexed locations

of

11,

16

and

16

for the dry-bulb, wet-bulb, and

calculated

vapor

pressure, respectively.

SECTION

12.

PROGRAM CONTROL

INSTRUCTIONS

c)

End loop

with

Instruction

95.

d)

Use

the

lf

Time lnstruction

(#92)

to

set

the Output

Flag every hour.

e)

Use

the

Average

Instruction (#71) with

5

repetitions starting

at

input location

21

to

average

the vapor

pressure over

the

hour.

The actual

keyboard entries for the examples

are shown below with the

first

examole

Instruction location equal

to

10.

The

lnput

Instructions

to

make

the

pressure and

temperature

measurements are assumed.

TABLE 12-3. Loop

Example:

Block

Data

Transform

Beginning

of

Loop

Delay

Loop Count

11: P57

WeUDry Bulb Temp to VP

01: 10

Pressure Loc

O2: 11--

Dry Bulb

Temp

Loc DRY

BLB#1

03: 16--

Wet

Bulb

Temp

Loc VP

#1

04: 21--

Loc

[:VP

#1

I

12: P95

End

10:

P87

01:

0

02:

5

13:

P92

01:

0

02;

60

03:

10

14:

P71

01:

5

02:

21

lf

time

is

minutes into

a

minute interval

Set high Flag

0

(output)

Average

Reps

Loc VP

#1

The

Loop with a delay may

be

used so that only

those

instructions within

the

Loop are executed

while certain conditions

are

met.

As a simple

example, suppose it is desired to execute one

set of instructions

from

midnight until

6

AM,

another set between

6

AM and

4

PM, and

a

third

set between

4

PM

and

midnight.

Between

6

AM and

4

PM, samples

are

desired

every

10

seconds;the

rest of the

time one

minute

between

samples

is

sufficient.

The execution

interval is set

to

10

seconds;

when

a

one

minute

sample

rate

is

desired, a delay of

6

(6

x

10s

=

60s)

is used

in

the

loop.

12-3

Campbell Scientific CR10 CR10 Measurement and Control - Page 159

Example

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