ROTRONIC MBW 373 - Manual (Page 22)

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2. All systems, including L and LX models, are equipped with controls for the head heater even
if not equipped with external tube heater controls. This is done to allow those systems to
automatically maintain the head temperature at or above 20°C as mentioned in the previous
note. If you enter a head heater setpoint, enable the control, and turn on the heater, you
may heat the head to values higher than 20°C. The main purpose for this ability is to allow
you to drive excess water from the measuring head if you suspect it of being wet for any
reason.
Cooling Control
Heat is generated by the cooling action of the Peltier element used for mirror temperature
control. Depending on the measurement range of the system, it will be equipped with an
air/water cooling combination or a refrigerant system. Air cooling is accomplished with a speed
controlled fan. Lower mirror temperatures produce more heat, resulting in increased fan speed.
Fan control is automatic and there are no user controls or adjustments for air cooling.
Water Cooling
Air cooled systems are also generally equipped with an auxiliary water cooling capability. If so
equipped, the left fixed key will be labeled Water Cooling. Pressing that key allows cooling
water to flow anytime the mirror is below a pre-specified temperature. When the mirror rises
above that temperature, water flow stops and air cooling resumes. You specify that temperature
with the Water Cooling key of the Control Setup menu.
Pre-Cooler (Refrigerated Cooling)
All 373L and 373LX Dew Point Mirrors are equipped with a refrigerant cooling system known as
the pre-cooler. The pre-cooler provides direct injection of refrigerant to the hot side of the Peltier
element. When equipped with a pre-cooler, the left fixed key will be labeled Pre Cooler.
Like the heaters discussed previously, the pre-cooler may be operated in either a fix or delta
mode. View or edit the current pre-cooler settings from the Pre Cooler key of the Control Setup
menu. As a general guideline, set the pre-cooler fixed mode temperature to a value that is
about 20 to 40°C higher than the dew or frost point of the gas being measured. Do not attempt
to measure gas with a dew or frost point that is higher than the fixed mode setting. If using delta
mode, about 30° is a good choice. In delta mode, the pre-cooler will automatically adjust
depending upon the value of the measured dew or frost point.
The refrigeration compressor is protected by a circuit breaker mounted on the back panel above
the power plug. You must ensure that this circuit breaker is ON for the refrigeration compressor
of the pre-cooler to operate. This breaker affects the pre-cooler’s compressor only and does not
affect power to any other part of the system.
Turn the pre-cooler ON/OFF from the fixed Pre Cooler key.
Changing Units
You can display system data in any of a wide variety of units. When you make a new units
selection, that selection remains until you change it again. To change units, follow the
instructions given in the Selecting Units section on page 6. Units selections are global across
the system, meaning that all values of that parameter type change to reflect the chosen units.
For instance, changing the temperature units to °C forces all temperature data to appear in °C.
Note:
Data retrieved via RS-232 will always be in SI units regardless of the units chosen for display.
Also note that settings within dialog boxes used for changing system parameters are also
entered and displayed in SI units. Units only affects the five data lines of the normal display
window.