ROTRONIC MBW 373 - Manual (Page 11)

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this is not required and nothing is wrong with leaving the Units menu (or any other menu) on
the screen.
The Measuring Head Assembly
The heart of the 373 Dew Point Mirror instrument is the
measuring head assembly. It is designed to be highly
sensitive and accurate, yet rugged and easily accessible for
periodic mirror cleaning. Although not required prior to initial
operation, you may wish to familiarize yourself with the
location and accessibility of the mirror and the other optical
components within this assembly.
For further discussion of the measuring head, and the mirror
cleaning procedure, refer to Mirror Cleaning on page 43.
Dew Point Measurement
When you power the 373 on, it begins in an idle state. In this state, it measures and displays
temperature, pressure, and flow transducers, but does not yet provide any meaningful humidity
related data. In order to provide humidity data (dew point, frost point, %RH, etc.), the Dew/Frost
Control mode must be enabled and gas must be flowing across the mirror. If %RH is desired,
note also that an external temperature probe must be connected. For external temperature
probe use, see External Temperature on page 23.
Starting / Stopping the Pump
Some gas flow is required over the mirror when measuring the dew or frost point temperature.
The nominal gas flow desired is approximately 20 to 60 liters/hour (0.2 to 1.0 liters/minute). If
your 373 is equipped with an internal gas pump, you can use it to provide the necessary gas
flow. If not, then you may need to provide for gas flow in some manner.
Use the Pump key on the bottom row of the touch screen to toggle the pump on/off. The Flow
Rate indicator on the status line should indicate that gas is flowing. The actual rate of flow is not
critical, but is best when within the limits previously mentioned. The gas flow may be adjusted
with an external valve, or by changing the pump control parameters. See Pump Control on page
17.
Notes:
1.
On the L and LX models, the gas inlet and outlet connections are generally capped for
transportation, or during periods of non-use, in order to keep the gas path dry. You’ll
need to remove these caps to allow for gas flow.
2. The L and LX models are generally not equipped with a gas pump and therefore some
alternate means of providing gas flow will be required for normal measurements.
(Although the measurements will most likely be inaccurate, operating without flow does
not harm the system. Therefore, you may continue on in this section even if your
system is not equipped with a pump.)
Pump
Flow Rate 60
30
0