OptiCal User’s Manual
Michell Instruments
17
OPTIDEW
4.1.2 Description of Screens 1- 8
Below is a description of the parameters and system status information shown on each
screen (see
Figure 16).
Screen 1
: Displays the status of the Optidew chilled mirror reference instrument
It will show
DCC, DATA HOLD, OPTICS ALARM
or
MEASURE
according to the current
status of the Optidew chilled mirror reference instrument.
Screen 2
: Peltier power and the Mirror condition
Peltier power indicates how much the heat pump is depressing in order to measure
the dew point. When the peltier power has a value of 100% and does not reduce over
an extended period of time, it means that the heat pump is at maximum depression.
In normal operation this indicates that the dew point is lower than the present mirror
temperature and therefore cannot be measured.
Alongside the peltier power value is an indicator that shows the control stability. When
this indicator shows
CNTRL
, it indicates the system is controlling the mirror temperature
on the dew point.
COOL
indicates the system is depressing the heat pump in order to
form dew on the mirror surface.
HEAT
indicates a rapid increase in dew-point level,
whereby the system needs to increase the temperature of the mirror surface to read
this new dew-point value.
The mirror condition indicates the amount of signal received back from the mirror which
includes both the level of moisture and contamination on the mirror surface. In
DCC
mode this display will only show the amount of mirror contamination and, if greater
than 80% after a
DCC
, will initiate an optics alarm condition.
Screen 3
: Humidity in %RH and ambient temperature
Screen 4
: Humidity in dew-point and ambient temperature
Screen 5
: Humidity in gkg
-1
and ambient temperature
Screen 6
: Humidity in gm
-3
and ambient temperature
Screen 7
: The
fi
rst line in this screen displays
Δ
(t – t
dp
). This is the difference between
ambient temperature and dew point. Note that this parameter will be equal to 0 if
the dew point is higher than the ambient temperature (e.g. during a
DCC
cycle). The
second line displays the ambient temperature.
Screen 8
: The
fi
rst line displays a
W
which is equivalent to %RH/100. The second line
displays ambient temperature.
