ROTRONIC MBW 373 - Manual (Page 19)

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4. Using the numeric keypad, enter the value needed. If the number shown in the Value
column is already correct, no entry is needed here. If you make a mistake while entering the
value, use the touch screen and press on the number in error. Each time you press the
touch screen there, the number will backspace one, erasing the flawed digits.
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.
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 373 operates. The control
setup capabilities are accessible through the Control Setup menu. See Navigating the Menus
on page 5.
Dew / Frost Control
The 373 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.
However, for mirror temperatures between 0 and approximately –30°C, the state of the
condensed layer is generally indeterminate since dew can, and does, exist on the mirror in a
meta-stable state at temperatures well below 0°C. In reality, the condensed layer on the mirror
could be dew, frost, or some combination of the two. Significant errors can result if wrongful
assumptions are made and can be in excess of 2°C.
To eliminate this problem, the 373 can automatically force all sub-zero condensation to a known
state of frost using the Force Frost function. Force Frost works by rapidly cooling the mirror
below –40°C forcing the condensate to solidify to a layer of ice or frost. The mirror will then re-
stabilize at the frost point temperature. Once the condensed layer is in a state of frost, it will
remain frost for all sub-zero mirror temperatures.
You can enable or disable the Force Frost function, and also decide at which temperature it
begins to work. From the Control Setup menu, press Dew/Frost Control (the top menu key).
Change the value of the Force Frost Below field. Mirror temperatures below this value will be
forced to frost.