ROTRONIC MBW 973 - Manual (Page 21)

System Configuration 17
Mirror Check Control
Mirror Check is the process of warming the mirror to evaporate all condensation, look for the
presence of contamination and account for it if necessary, then re-initiating a new dew or frost
point measurement. Mirror Check may be initiated manually with the fixed Mirror Check key, or
if enabled to do so, it may trigger automatically at pre-specified time intervals. During a mirror
check function, whether triggered automatically or manually, the fixed mirror check key indicates
red while heating, brown while holding at the high temperature, then yellow while allowing the
mirror to cool to reform the dew or frost layer again. Once the system has again established a
dew or frost layer, and become stable at that value, the mirror check function is complete and
the color indications are removed. To view or edit the Mirror Check parameters, press the
Mirror Check key of the Control Setup menu.
Cycle Time
If Automatic Mirror Check is desired, enable it by pressing the Cycle Time button. A green light
on the Cycle Time button indicates that automatic mirror check is enabled. Even if automatic
mirror check is not enabled, manual mirror check may be initiated at any time simply by pressing
the fixed Mirror Check key at the bottom of the screen. When automatic mirror check is
enabled, the fixed Mirror Check key also displays a countdown timer indicating the time until the
next automatic mirror check function.
Changing the Cycle Time changes the time interval between automatic mirror check operations.
Heating Time
The Heating Time determines how long to hold at the mirror check temperature before allowing
another dew or frost point measurement. A heating time of 0 results in no hold, meaning that
once the mirror check temperature has been reached, the function ends and dew/frost control
resumes immediately. If a heating time greater than 0 is entered, then the mirror will heat and
remain at that temperature for the duration of the heating time value. Heating time is effective
regardless of whether mirror check was triggered automatically or manually.
Heat To
Edit the Heat To field to change the temperature that the mirror will be heated to, and optionally
held at, during Mirror Check.
Pump Control
The pump, if your system is so equipped, is a diaphragm type driven by a brushless DC motor.
Pump speed, and thus flow rate, is controlled by changing the amount of power applied to the
motor. Pump power can be set from 0 to 100%, accessed through the Pump key of the Control
Setup parameters menu. When connections to the system are made with short tubing of ¼”
diameter resulting in very little flow restriction, settings for pump power of 10 to 25% are often
acceptable. However for long tubing runs, small tubing diameters, or when restrictions are
induced (by externally installed flow meters for instance) higher pump power settings may be
required. Experiment to determine the lowest pump power setting needed to obtain the desired
flow rate. Turn the pump on and off with the fixed Pump key.
Depending on your system configuration, a pump may not be needed. Or if a pump is installed,
it may not necessarily need to be enabled if you are sampling from a positive pressure system.
The pump, if installed, is configured with forward flowing check valves that open easily. This
allows even a slight positive pressure to be used flow gas through the head, even if the pump is
installed but not enabled.