Super Systems DP2000 - Manual (Page 5)

SSi Super Systems Inc.
Product Manual - Model DP2000 Portable Dew Point Analyzer
SSi Manual 4545 – DP2000 Super Systems, Inc. Page # 5 of 17
Revision Level “F” (800 ) 666-4330
furnace or generator is operating normally, residual moisture may still be present in the
sample tube or plumbing system. In the same way that the ports are checked for soot (see
above) they should be checked for moisture before attaching the instrument. This is
especially important when taking a sample from a generator, since the sample port is
usually preceded by a significant amount of plumbing. All traces of moisture should be
eliminated before attaching the instrument. Failure to do so will result in erroneous
measurements and could result in damage to the analyzer.
The first signs of moisture in the instrument will be visible condensation in the sample
tubing and an unusually high dew point. The upper range of the sensor is +80°F, so if
that value is displayed on the instrument it is probably due to the presence of moisture. If
this moisture is not removed, it will cause the sensor tip to corrode and will eventually
require the sensor to be replaced.
To remove moisture from the instrument, the sample tubing and filter should be removed
from the instrument since they will probably be wet. An inert gas such as Nitrogen or
Argon should then be flowed through the instrument (with the pump off) for as much
time as it takes to dry out. This dry-out time will depend on the amount of moisture
present in the instrument. The condition of the sensor can be monitored by periodically
reading the dew point from the display and watching the value decrease over time. To
test if it is operating properly, verify the ambient dew point against a web-based weather
station that will report the ambient dew point for your area. If the displayed reading is
within three degrees of the reported dew point when the instrument is taken outside, then
all of the moisture has probably been successfully removed. The wet filter and sample
tubing can be re-attached after they have been completely dried out.
To prevent the possibility of moisture damaging the instrument, be sure that the measured
dew point is below ambient levels before it is stored. If necessary, Nitrogen or Argon can
be used to dry out the instrument after use.
WHAT IS DEW POINT?
Dew point can be defined as the temperature at which the water vapor pressure of the gas
equals the saturated water vapor pressure. In other words, it is the temperature at which
condensation will just begin to occur as the gas is cooled. Dew point and relative
humidity are not the same measurement. Relative humidity is the amount of water vapor
in the air compared to the amount the air could hold if it was totally saturated, and it is
expressed as a percentage, not a temperature. To determine dew point, two main
variables are required: Relative Humidity and Temperature. The DP2000 measures both
variables to compute the displayed dew point.
HOW IT WORKS –
The dew point sensor is a “dielectric ceramic” that varies its electrical capacitance with
changes in relative humidity. The sensor is mounted in a short probe, which is installed
in a T-fitting that allows the sample gas to flow past the sensor. The tip of this probe