Kahn Optisure Remote, User Manual

Page: 37 / 54

Optisure Remote User’s Manual
30 March 2018
OPERATION
• Whether the instrument is controlling by switching MAXCOOL on for a short
period and then switching back to MEASURE. This will depress the mirror
temperature briefly and when it is switched back to MEASURE the control
loop should be able to stabilize the mirror temperature at the dew point
again.
The MAXCOOL function can be turned on by touching the MAXCOOL button on the Main
Screen.
4.5.3 Frost Assurance Technology (FAST)
In carefully controlled laboratory conditions, super-cooled water can exist in temperatures
as low as –48°C. However, when using a chilled mirror instrument it only occurs on the
mirror at temperatures down to around –30°C.
A gas in equilibrium with ice is capable of supporting a greater quantity of water vapor
at a given temperature than a gas in equilibrium with liquid water. This means that a
measurement below 32°F (0°C) taken over water will read approximately 10% lower
than the same measurement taken over ice.
Following DCC, the Optisure Remote makes an initial dew point measurement. If the
initial measurement is b26°F (-3°C) and -40°F/C then the mirror is driven down
to below -40°C to insure the formation of ice on the mirror surface. The instrument then
continues operation as normal.
Note that Data Hold is active whenever FAST is active.
For further information, see section 4.5.3.
4.5.4 STANDBY Mode
In STANDBY mode, drive to the Peltier heat pump is disabled. The main use for this
feature is during set up (when measurements are not required), i.e. when flow rates are
being adjusted and the analog outputs are being configured.
4.5.5 Parameter Conversions & Pressure Compensation
Many parameters which are calculated by the Optisure require a temperature or pressure
reading in addition to dew point to insure the calculated value is correct.
These additional readings can either come from a sensor connected to the Optisure, or
from a fixed (manual) input. See section 2.5.9 for details on external inputs.
Calculated Parameter Temperature input required Pressure input required
%RH
 
g/m
3
 
g/kg
 
ppm
V
 
%Vol
 
Table 12
Calculated Parameters
If external sensors are used to generate the inputs, then the sensors should be positioned
with so that they are making a measurement representative of the environment seen by
the dew-point sensor.
4.5.6 Data Logging
The data logging function allows all of the measured parameters to be logged at a
user specified interval on the supplied SD card via the SD card slot on the base or side
of the instrument. The filename for each log file is generated automatically from the
instrument date and time.