Campbell 21X Instrukcja Operatora Pobierz pdf (Strona 95)

SECTION

9. INPUT/OUTPUT

INSTRUCTIONS

The

count is incremented when

the input

voltage

changes

from below 1.5

volts

above

3.5 volts.

The maximum

input

voltage

t20

volts.

LOW

LEVEL

This

mode

is used

for

counting

freqqency

signals from

magnetic

pulse

flow

transducers

other

low voltage,

sine wave

outputs.

MINIMUM

AC INPUT VOLTAGE:

6 millivolts

RMS

INPUT HYSTERESIS:

11 millivolts

MAXTMUM

AC INPUT VOLTAGE:

20 volts

RMS

FREQUENCY RANGE:

Input

Voltage

(RMS)

Range

20 millivolts

1 Hz

to 100

miflivolts

0.5 Hz

to 4OO

150 millivolts

to 20

volts 0.3 Hz to 1000 Hz

(consult

the factory

if higher

frequencies

are

desired)

SWITCH CLOSURE

this configuration, the minimum

switch

closed time is

3 milliseconds. The minimum

switch

open time is

milliseconds.

The

maximum

bounce time

is 1

millisecond

open

without

being counted.

The

pulse

count input channels

each have

eight bit counters.

Input

frequencies

greater

than

2550

(the

limit of

the eight bit

counter,

255

counts

at the reset interval

of 0.1

second)

can be counted

by combining two

counters

one

input

channel. When this

option is

selected,

channel 1 or 3 is

specified

parameter

2 and

the

input is

connected

either

channel 1

or 3.

f n this case,

either channel2 or 4

or both are not

used. One may

use 2

sixteen

bit

pulse

count

channels or a

combination of 1 sixteen

bit

counter and 2

eight bit counters.

(Campbell

Scientific

has

a hardware and software

modification

that

changes

the reset

interval

0.0125 seconds

allowing

greater

input frequency

with

the 8 bit counters

(2551.0125=20.4kHz\.

Pulse measurements

with

this modification

will

not work when

voltage

measurements

are made

with the

"slow"

integration. Consult

the factory

for additional information.)

Every

0.1

seconds,

the 21X

processor

transfers

the values

f rom

the

8 bit

pulse

counters

into 16

bit accumulators

(maximum

count

65,535)

and the

bit counters

are

hardware reset

zero.

The

pulses

accumulate

these

16 bit

accumulators until the

program

table containing

the Pulse

Count instruction

executed.

the

beginning of the

execution of

the

Table

containing the Pulse

Count instruction, the

total

the 16 bit accumulator is

transferred

temporary

RAM

buffer. The 16

bit

accumulator

then zeroed.

When

the table

execution

reaches

the

Pulse

Count instruction, the value i

the

RAM

buffer

is multiplied

by the

multiplier

added

to the

offset

and

placed

into the

designated Input Memory location. The RAM

butJer does

NOT accumulate

counts:

it is

each time

the

table is executed

regardless of

whether or

not

the

pulse

instruction

executed.

allcounts

are necessary,

imperative that

the Pulse Count

instruction

executed

(not

branched around) every time its table

executed.

a table execution

was

skipped because the

processor

was executing the

table

(Section

2.1), the

value in

the 16 bit

accumu

the result of a

longer

than normal

interval.

This

value

can

either be used or it can be

discarded.

pulse

counts are

being

totalized, a

missing

count

could be

significant

and the value

from the

erroneously

long interval should NOT

be discarded. lf the

pulse

count is

being

processed

a way in which

the resultant

value

is dependent upon the

sampllng interval,

the

value

from

the

excessive interualshould be

discarded. lf the value is

discarded

the value in

the RAM buffer

from

the

will

be used.

There is

also

an option

to output the

count

as a

frequency

(i.e.,

counts/execution interual in

seconds

Hz)

as well

as discard the

result

excessive

interval. This

allows

the

use of a

conversion factor that is independent of

the

execution interval.

When

datalogger time is changed,

whether

through the

keyboard

or with a

telecommunications

program,

partial

automatically done to resynchronize

program

execution with

real

time. The resynchronization

process

resets the

pulse

accumulation

interval

resulting

in an

interualwhose

length can be

9-2

1 2 ... 90 91 92 93 94 95 96 97 98 99 100 ... 190 191

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