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ovl.2
EXCITATION OUTPUTS
The first fou numbered
terminals on the lower
are
the SWITCHED EXCITATION
terminal
supply programmable
for resistive bridge
ts.
The excitation channels are
only
on during
the rneasurement.
ovl.3
ANALOG OUTPUTS
The
two Codtinuous Analog Output (CAO)
channels suSply continuous output voltages,
under program control,
for use with strip charts,
X-Y plotters,
or proportional controllers.
OV1.4
DIGITAI..J
CONTROL PORTS
The six
DIGI1TAL
CONTROL PORTS
(0
or
5
volt states) allow on-off
controlof
external
devices. Thfse
control
potts have
a
very
limited curreht
output (5 mA) and are used to
switch solid
State
devices which
in
turn provide
power
to
rel{y coils (Section
14.4).
OV1.5 PULSE
OOUNT INPUTS
The
four PULSE COUNT INPUTS measure
contact
clos{re,
low
levelAC, or high frequency
pulse signal$.
periods
in
the field.
OV2.
M
AND PROGRAMMING
coNc
The 21X
be
programmed before
it
will
A program consists
.
21X
MICROLOGGER OVERVIEW*
table. The
program
table is given an execution
intervalwhich determines how frequently that
table is
executed.
When the
table is executed,
the instructions are executed in sequence from
beginning to
end.
After executing the table, the
21X waits
the remainder of the execution
interval and
then executes the table again
starting
at
the beginning.
The interualat which the table
is
executed will
generally determine
the intervalat which the
sensors
are measured. The interval at which
data are stored is separate
and may range from
samples every
execution interval to processed
summaries output hourly, daily, or
on longer or
irregular intervals.
Figure
OV2-1 represents the measurement,
processing, and data storage
sequence
in
the
21X and shows the types
of instructions used to
accomplish
these tasks.
OV2.1 INTERNAL
MEMORY
The
21X has 40,960 bytes of Random Access
Memory (RAM), divided into five
areas.
The
five areas of RAM are:
1.
Input Storage -
Input
Storage holds the
results
of measurements or calculations.
The *6 Mode is used to view Input Storage
locations to
check current sensor readings
or calculated
values. lnput
Storage defaults
to
28 locations. Additional locations can
be
assigned using the
"A Mode.
2.
Intermediate Storage
-
Certain Processing
Instructions
and most of the Output
Processing Instructions maintain
intermediate results in Intermediate
Storage. Intermediate storage
is
automatically
accessed
by
the Instructions
and cannot be
accessed
bythe user.
The
default
allocation
is
64 locations. The
number
of locations can be changed using
the
*A Mode.
channels.
excitation
make any
of
a
group
instructions
entered into a program
connection tb the
21X power
supply. The
+12
and ground ferminals
can be used to connect
an
external
f
2
volt battery to the 21X
to
ov-3
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