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PROCESS OPERATOR COMMUNICATIONS
SURVEY
Generally, process operators use special
consoles for entering information into the computer
and for requesting various special functions from
it. These work out better than
I/O
typers because
it is much easier to use them correctly.
The computer communicates with the operator
by outputting on several electric typewriters.
Usually, one typer is devoted to message and alarm
print-outs and several more, to normal and spe.6'ial
log print-outs of measured and calculated values.
Occasionally, in installations involving multiple
·process units and a great deal of historical logging,
a line printer at a central
location
will also be used,
though even an electric typer can print information
faster than most men can read it and act on it.
In applications where an operator must review
a fair amount of data but where printed copies are
not required, the GE Data-Edit Display may be
preferable.
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Figure 10
STANDARD OPERATOR'S CONSOU
Referring
to the console in Figure
19,
the top
display
is
a
decimal,
engineering
units display
of
a selected
point.
Any sensor or calculated value
may be
displayed, through
operator selection.
The
top row of
the
"demand
function" lights,
(a
10
x
10
back-lighted matrix)
is used
for
system
alarms.
These
alarms are displayed
in
red and
typically
indicate
such conditions
as:
Stall Alarm
-
the
light
indicates that the com-
puter is
in a
program loop, (stalled),
or
that
a
hardware
failure
has
occurred
to stop
sequencing.
High Temperature - The light occurs when the
cabinet temperature exceeds predetermined
limits.
Peripheral Trouble - The
light
occurs
if
the
.
.
computer tries to use a peripheral that will
not operate.
Analog Check Point - The light occurs
if
the
accuracy of reading a precision voltage is less
than a predetermined value (0. 1 to 0. 2%).
Off Limits Alarm
-
The light occurs whenever
a point is out of limits. As long as any values
are in alarm, the alarm light will remain on.
The remaining rows of function lights are
numbered by row and column, and contain a de-
scription of the function. For example, the third
row and tenth column in Figure
10
is the
"enter
data" demand function, and is labeled as follows:
10
ENTER
DATA
FVMA
The operator determines the desired function
and dials the function identification (10 in the above
example) into the
"function"
thumb-wheel switches.
The operator must then tell the computer what
"value"
is to be entered pertaining to what point
("point identification"), and what action is desired
(storing) this value by dialing the appropriate thumb-
wheel switches. Since the
"enter
data" function will
change a location in memory, the
"memory
change"
back-lighted pushbutton will light, reminding the
operator that it must be pushed before the "action"
pushbutton is activated. This is one of numerous
s~feguards.
Options
The
standard GE
/
PAC
4000 console offers
several options. In the examples above,
the
oper-
ator would have to select a
demand
function which
would cause type-out of the
point
identification of
the
value being displayed. A second
decimal display
may
be added for point
identification.
Both
the point
identification
and
digital value
displays
may be eliminated, at the
expense
of
operator inconvenience.
In such
a configuration, the
operator would
then be required to use demand
functions and
type-out in two steps to
obtain
identifi-
cation
of the point and
its
value.
37
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