ROTRONIC MBW 973 - Manual (Page 19)

System Configuration 15
5. Once the value is shown is what you want press the Ok button (or the enter key) to accept
the new value, or press the Cancel button to abort all changes made to the mode and to any
values.
The only values that get accepted by the system are those that correspond with the selected
mode. In other words, if you change the value of the Autoscale Minimum, but Fixed Range is
the selected mode, the Autoscale Minimum value remains unchanged.
Time Span
Changing the time span allows you to see a longer or shorter history period for the data. The
973 stores a fixed number of data points independent of the selected time span. Changing the
time span changes the interval used for data storage. With a 15 minute time span, the graph
data is sampled and stored every few seconds. However, with a 2 hour time span, the graph
data is only sampled, stored, and updated about once a minute.
When you change the time span, the old data previously sampled and stored at the old interval
will be incrementally replaced by new data sampled at the new interval. The Time Span as
indicated on the graph will always reflect the actual time span of the currently stored data, and
will eventually agree with the time span you select. Regardless of the graph selected, the
selected time span is common to all graphs so that they all have the same time relationship to
one another.
The result of a time span change might not be seen instantaneously. It will take some time for
the old data at the old time interval to be replaced by data at the new time interval as
determined by your selected time span.
Viewing Data both as Numeric and as a Graph
Since all displayable data may be viewed either numerically or as a graph, it does not matter
which parameters are selected on which lines of the display. Often times you may even want to
select the same parameter on two different data lines. That way you can have one of them set
for numeric mode and the other one showing you a graph of that same data.
Control Setup
With the Control Setup, you can control the manner in which the 973 operates. The control
setup capabilities are accessible through the Control Setup menu. See Navigating the Menus
on page 6.
Dew / Frost Control
The 973 can control on either dew point or frost point, and has the ability to distinguish the
difference through a function known as Force Frost. The Dew / Frost Control setup menu is
used to control the Force Frost function and also allows for setup of the ORIS (Optimal
Response Injection System) operation.
Force Frost Below
For mirror temperatures above 0°C, water vapor condenses on the mirror as liquid water (dew).
A condensation layer resulting from a mirror temperature above 0°C is considered a dew point.
For mirror temperatures far below 0°C (generally mirror temperatures below –40°C), water
vapor condenses on the mirror as solid ice (frost). A condensation layer resulting from a mirror
far below 0°C is considered a frost point.