ROTRONIC MBW 973 - Manual (Page 13)

Getting Started 9
The Measuring Head Assembly
The heart of the 973 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 37.
Dew Point Measurement
When you power the 973 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 22.
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 973 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.
Measuring the Room Ambient Dew Point Temperature
Enable Control
Lets use the 973 to measure the dew point temperature of the room by enabling the portion of
the system responsible for cooling and maintaining the mirror at the dew or frost point
temperature. Do so by pressing the Dew/Frost Control key. When enabled, a green bar on
the key illuminates and any dew or frost point temperature indication begins to drop as the
mirror cools toward the dew or frost point temperature. See Selecting Parameters to Display on
page 6 to select one of those parameters for display.
What You’ll See
When the Dew/Frost Control is enabled, have a look at the Status Bar (if you have your screen
set up to show it). The Status Bar has visual bar graphs that represent Balance, Density, Mirror
Residue, and Flow Rate.
Pump
Dew/Frost
Control
Flow Rate 60
30
0