GDS C1, Instruction Manual

Page: 8 / 56

C1 Controller Users Manual
Revision 4.6
3
1.1.1 TREND SCREEN
The C1 Trend screen shown in Figure 2.0 displays a 24 hour trend of input data for the
channel selected. Horizontal tic marks are each hour and vertical tic marks are each 10%
of full scale. Dashed lines indicate alarm levels. The graphic LCD is 240 pixels wide so
each pixel represents 1/10 hour, or 6 minutes worth of data. The trend is 100 pixels high
so each represents 1% of full scale in amplitude. Since each data point must be collected
for 6 minutes before it may be displayed, it is likely input values will fluctuate during this
interval. Therefore, MAX, MIN and AVERAGE values are stored in RAM memory for
each 6 minute subinterval. To accurately portray the trend, a vertical line is drawn
between MIN & MAX values for each 6 minute subinterval. The AVERAGE value pixel
is then left blank, leaving a gap in the vertical line. This is demonstrated in the
noisy area
of the 24 hour trend in Figure 2.0. If the MAX & MIN values are within 2% of each
other there is no need for the vertical line and only the AVERAGE value pixel is
darkened as in the
quiet areas.
The top portion of each trend screen indicates channel #, real time reading in engrg. units,
measurement name, range, and MIN, MAX & AVERAGE values for the preceding 24
hour period. The SI field on the top right indicates number of seconds remaining in the
current 6 minute subinterval.
1.1.2 BAR GRAPHS SCREEN
The C1 Bar Graphs screen shown in Figure 2.0 allows all active channels to be viewed
simultaneously. Both engineering units values and bar graph values are indicated in real
time. Lines across the bars indicate the alarm trip points making it easy to identify
channels at or near alarm. A feature in the Systems menu tree allows new alarms to
always force the LCD to the bar graphs screen. This is useful for applications requiring
channels with alarms to be displayed.
1.1.3 COMBINATION SCREEN
The C1 Combination screen shown in Figure 2.0 offers a view of a single channel but
displays the data as a 30 minute trend, bar graph and large engineering units. It is also
useful for testing inputs for stability since MAX, MIN & AVERAGE values refresh each
time this screen is selected. For example, to test stability over a one hour period for an
input, begin timing as soon as the channel is selected. One hour later record the MAX,
MIN & AVERAGE values. The difference between MAX & MIN indicates peak to peak
excursions over the one hour period and AVERAGE is the average for the hour. Longer
or shorter tests may also be run. The numeric value shown below the bar-graph indicates
number of minutes samples have been taken. After 999 minutes the AVERAGE buffer
overflows and the error message
UPDATE appears in the AVERAGE field. Exiting this
screen resets the buffer and clears the error message.