169/2005

169/2005
169/2005
Update on the CassiniHuygens Mission
Vaisala Leads the Way
Towards Understanding
Humidity Conditions
in Cold and Humid
Atmospheres
Free Air CO2 Enrichment
Experiment in
Northern Japan
Modernizing Weather
Information Networks
in Mexico
Contents
3
Vaisala Leads the Way Towards Understanding Humidity
Conditions in Cold and Humid Atmospheres
4
Vaisala INTERCAP® Humidity and Temperature Probe
HMP50 in Airborne Measurements
7
Introducing Vaisala HUMICAP® Humidity and
Temperature Transmitter Series HMT100 - New Flexibility
in Demanding HVAC Applications
8
Update on the Cassini-Huygens Mission
9
DORIS - Doppler Orbitography and Radiopositioning
Integrated by Satellite
When the Huygens
probe successfully
landed on Titan,
one of Saturn’s
moons in January
2005, it carried eight
Vaisala BAROCAP®
barometric pressure
sensors on board as part
of one of its six science
instruments. Page 9.
The Technical Research
Centre of Finland
and the Finnish
Meteorological Institute
have recently carried
out measurements in
arctic severe weather
with the heated Vaisala
HUMICAP® Dewpoint
Transmitter HMP243,
and compared the
results with those
achieved with more
conventional probes.
Page 4.
11
Japan Meteorological Agency Adopts Vaisala Barometers 12
Studying the Changing Climate in Controlled
Environment Chambers
13
Free Air CO2 Enrichment Experiment in Northern Japan
15
Safety First in CO2 Production
17
Modernizing Weather Information Networks in Mexico
19
US National Weather Service Chooses Vaisala’s
Modified Version of the Vaisala WINDCAP® Ultrasonic
Wind Sensor WS425 as Part of Its Nationwide Surface
Observation System
22
Factors Affecting Water Solubility in Oils
24
Long-Term Stability and Low Maintenance: Dewpoint
Measurement at Its Best
26
Vaisala DRYCAP® Dewpoint Transmitter DMT340 Versatile Installation Options for Dewpoint Measurement 27
Briefly Noted
Vaisala in Brief
– We develop, manufacture and
market products and services
for environmental and industrial measurements.
tion, improved safety and better
performance.
Editor-in-Chief:
Marikka Metso
Design and Artwork:
Sampo Korkeila
Publisher:
Vaisala Oyj
P.O. Box 26
FIN-00421 Helsinki
FINLAND
Printed in Finland by
Edita Prima, Finland
Phone (int.):
+358 9 894 91
Internet:
http://www.vaisala.com
2
169/2005
V
EN
IRONMEN
T
EL
Telefax:
+358 9 8949 2227
ISSN 1238-2388
LA B
– We focus on market segments
where we can be the world leader,
the preferred supplier. We put a
high priority on customer satisfaction and product leadership. We
secure our competitive advantage
through economies of scale and
scope.
Cover photo:
Cassini during the Saturn Orbit Insertion
maneuver, artist’s concept. Courtesy NASA/JPLCaltech.
AL
– The purpose of these measurements is to provide a basis
for a better quality of life, cost
savings, environmental protec-
29
What is the fate of
our forests in a world
with an increased
atmospheric CO2
concentration? The Free
Air CO2 Enrichment
(FACE) experiment
hopes to provide
some answers to these
questions. Page 15.
NORD
IC
President’s Column
441
002
Printed matter
President’s Column
Premium Class Value
I
f an organization’s success is
dependent on the quality of
its environmental measurements, then very strict criteria
must be applied to the selection
of measurement equipment. This
is particularly true in environmental research, for example. In
operational meteorology, excellent service is only possible with
high-quality observation data. In
terms of industrial or industrial-
type processes, it is often possible to radically improve the quality and yield of these processes if
one can measure the state of the
immediate environment and control its parameters.
Vaisala seeks customers who
want premium class value. In
short, this is our value proposition. It has three important components: innovation, reliability
and solutions.
A premium class product or
service is often unique in its concept, technology, structure, materials or process steps. This is
achieved through innovation –
through creative people with excellent and complementary skills
working together and discovering something new. For a company, this means investment in research and development. We invest 12% of our annual net sales
in R&D.
Reliability means many
things for the end-user. Measurements need to be accurate, stable and selective. Data availability must be good. Maintenance
intervals should be long. Deliveries must come on time. Spare
parts should be available. With
respect to system products, it is
important to be able to supply
upgrades and extensions, as they
extend the lifetime of the investment. Behind all these reliability features are corporate ethics.
Vaisala’s reliability stems from its
corporate values of “fair play”
and “customer focus”.
Customers can seldom articulate their exact needs in the
form of product specifications.
It is also hard to keep track of
what is available. Our level of expertise is shown by how well we
understand the customer’s situation – no matter whether it is expressed in business terms or technical terms – and how quickly we
can find the best solutions. If we
succeed in solving the customer’s problem, we can be sure that
they will come back to us. Therefore, we recognize the need to
continuously develop our competence in customer applications. Good customer contacts
help us in this.
A value proposition is always
connected to company culture.
Over the years we have had the
opportunity to work with very
demanding customers. This has
shaped our company culture to
match our value proposition:
premium class value. ●
Pekka Ketonen
President and CEO
169/2005
LasseMakkonen
Ph.D.,SeniorResearchScientist
VTTTechnicalResearchCentreofFinland
VaisalaLeadstheWayTowards
UnderstandingHumidityConditions
inColdandHumidAtmospheres
The Technical Research Centre
of Finland (VTT) and the Finnish
Meteorological Institute (FMI) have
recently carried out measurements
in arctic severe weather with the
heated Vaisala HUMICAP® Dewpoint
Transmitter HMP243, and compared
the results with those achieved with
more conventional probes. The results
have been published in the BoundaryLayer Meteorology journal.
T
he data indicate that problems that have hampered
all previous humidity
measurements under such conditions can be solved with the
HMP243. Furthermore, contrary to a cooled-mirror sensor,
the HMP243 shows saturation
with respect to ice during snowfall, as one would expect.
4
169/2005
Collecting data at
freezing temperatures
While measuring humidity is
generally quite accurate, problems arise in severe weather, particularly at freezing temperatures.
The main reason is that the probe
will ice up due to sublimation, after which its reading will be fixed
to the humidity that corresponds
to the frost point [1, 2]. It is also
important to understand humidity in cold temperature and high
humidity conditions, in order to
understand and predict the icing of wind turbines and instruments, hoarfrost, cloud physical processes and the global heat
balance of the Earth in the polar areas.
The widely used Vaisala Humidity/Dewpoint Transmitter
HMP233 is based on the Vaisala
HUMICAP®, a capacitive polymer film probe sensitive to relative humidity. The HMP243, on
the other hand, uses a different
measurement principle. While
the humidity sensor element is
a capacitive polymer film based
on the HUMICAP®, the device
is fundamentally different in that
the probe itself is heated a few degrees above the ambient air temperature in order to prevent sublimation. A Pt100 thermo-element
is attached to the humidity sensor head for measuring its temperature Ts. The device includes
a separate unheated thermometer
installed far away from the heated
probe. The unheated thermometer measures the ambient air temperature Ta, which makes it possible to calculate the relative humidity RH. On the new Vaisala
production line, the corresponding product is the Vaisala HUMICAP® Humidity and Temperature Transmitter HMT337.
The measurements discussed,
which can be seen in more detail
in the Boundary-Layer Meteorology journal, were carried out on
two mountain fells in Lapland.
The sites were partly manned
during the measurements, so that
the instruments could be carefully monitored and ice occasionally cleaned from the radiation
shields of the hygrometers. Manual observations were also made
of the liquid water content and
droplet size of the icing clouds
using the rotating multicylinder
method [5]. Video recordings
and Labko LID ice detectors [6]
were used, which made it possible to detect events of rime icing
and snowfall.
Instrument
comparisons
The correspondence of RH as
measured with the HMP233 and
HMP243 on Olostunturi fell is
shown in Figure 1. Strikingly,
points with RH ≥ 100%, that is,
air at or above saturation with respect to water, are completely absent from the data of the HMP233.
They are abundant, however, in
the data of the HMP243. This
suggests that the HMP243 is able
to detect in-cloud conditions and
icing situations contrary to the
conventional sensor.
Secondly, the HMP233 and
HMP243 measured RH in excellent agreement up to RH around
60% at Olostunturi. This shows
that the instruments measure
consistently and that their calibrations, at least in this range of
RH, are good. Problems arise at
higher humidity levels and become more serious close to RH
= 100%. Apparently, the points
in Figure 1 where the HMP243
shows a much higher RH are due
to ice cover on the sensor of the
other probe. Such ice cover may
persist a long time after its formation even at low subsequent humidity, unless the air temperature
rises above 0 ºC. Consequently, a
conventional capacitance probe
shows too high RH when still
iced up, even though the air is
no more saturated with respect
to ice, and a too low value when
being iced up in air that is actually supersaturated with respect
to ice. In the latter case the reading is fixed at RHi = 100%. Here
RHi is the relative humidity (as a
percentage) with respect to ice
RHi(Ta)=[ew/esat,i(Ta)]100
where esat,i(Ta) is the saturation
water vapor pressure with respect
to ice at the temperature Ta.
Figures 2 and 3 show the
relative humidity with respect
to ice, RHi versus air temperature Ta as measured with the
HMP233 and HMP243 respectively. Figure 3 reveals a very different picture from Figure 2. Because of the measurement principle that prevents sublimation
on the probe, the HMP243 appears to measure properly, both
in supersaturated conditions as
well as in dry air that follows
such conditions. Consequently, Figure 3 shows thousands of
data points where RHi > 100%,
whereas there are only a few such
points measured at any temperature with HMP233 in Figure
2. From the simultaneous icing
observations and measurements
of cloud microphysical properties, we know that the supersaturated conditions measured
with the HMP243, but not those
measured with the HMP233, are
real.
The results thus indicate that
the HMP243 with heated probe
is able to avoid the errors associated with icing on conventional
hygrometers.
Vaisala probe more
accurate than the WMO
recommended standard
As the new field data strongly supports the validity of the
humidity measurements of the
HMP243, one would expect that
it would agree well with the data measured with a cooled-mirror hygrometer, which is recommended as standard by the
WMO [7]. However, Figure 4
demonstrates that this is not the
case at all at low temperatures.
The results in Figure 4 indicate that at cold temperatures there is something seriously wrong with the humidity measurements of either the HMP243,
the cooled-mirror hygrometer, or
both. This question was investigated further by separating in the
data the cases of in-cloud icing,
no icing, and snowfall based on
the ice detector output and the
video recordings. This is shown
in Figure 5. An important ob-
Following [3], the principle of the HMP243 is
as follows:
The relative humidity RH (as a percentage) is defined by
WMO with respect to water, i.e.
RH(Ta )=[ew /esat,w(Ta )]100
(1)
where ew is the water vapor pressure in air and esat,w (Ta )
is the saturation water vapor pressure with respect to water at the temperature Ta. From (1), the ambient water vapor pressure is
ew =[RH(Ta)/100]esat,w(Ta)
(2)
On the other hand, because (1) is valid at any T, it may be
applied at the temperature Ts of the heated polymer sensor as well, so that
ew =[RH(Ts)/100]esat,w(Ts)
(3)
From (2) and (3) it follows that
RH(Ta) = [esat,w(Ts)/esat,w(Ta)]RH(Ts)
(4)
The HMP243 probe determines RH(Ts ), since it measures the
heated sensor’s capacitance C and temperature Ts directly and the response function C(RH,Ts ) for the sensor is well
known from experiments. Using the measured Ta and Ts the
saturation water vapor pressures in (4) can be determined
since the function esat,w (T) is known. Thus, the ambient relative humidity RH(Ta ) can be calculated from (4).
The ingenious use of (4) as the measurement principle
of HMP243 escapes the problems of sublimation because (4)
is valid at any temperature of the sensor head. Consequently, the humidity probe as a whole can be heated sufficiently
to keep Ts well above Ta , so that the probe is ice-free at all
times, and yet still obtain an accurate RH value for the undisturbed ambient air. ●
Figure 1: Correspondence of the relative humidity RH as measured
with the HMP243 and HMP233. The linear correlation coefficient is
0.967.
169/2005
Figure 2: Relative humidity with respect to ice RHi as measured with
the HMP233 versus air temperature.
Figure 3: Relative humidity with respect to ice RHi as measured with
the HMP243 versus air temperature.
March 2002, Luosto
Air temperature -10…-26 °C
120
200
180
100
160
RHi (%), HMP243
THY, RH (%)
140
120
100
80
RHi, no icing
80
RHi, icing
RHi, snowfall
60
60
40
40
20
0
20
0
20
40
60
80
100
120
140
160
180
200
HMP243, RH (%)
-20
-15
-10
-5
0
5
Air temperature (°C)
Figure 4: Correspondence between relative humidity as measured
with a cooled-mirror hygrometer and the HMP243 when the air
temperature is below -10 °C.
Figure 5: Relative humidity with respect to ice RHi versus air
temperature as measured with the HMP243. Icing events are shown
in blue and snowfall events in yellow. (Figure by K. Säntti, Finnish
Meteorological Institute).
servation is that the HMP243
shows values very close to saturation with respect to ice during snowfall at all temperatures.
Such equilibrium is to be expected, because, in snowfall, the concentration of ice particles is high
and their surface area to bulk
volume ratio is large. The corresponding data for the cooledmirror hygrometer did not show
this behavior, suggesting that results measured with the Vaisala
HUMICAP® Dewpoint Transmitter HMP243 reflect the real
humidity conditions under these
circumstances better than the
sensor recommended as a humidity measurement standard by
the WMO.
Possible reasons for the poor
behavior of the cooled-mirror
device include the observation in
REFERENCES
[1] L. Makkonen, L., “Comments on
“A method for rescaling humidity
sensors at temperatures well below
freezing”, J. Atmos. Oceanic. Technol. vol. 13, pp. 911 - 912, 1996.
[2] J. C. King, and P. S. Anderson, “A
humidity climatology for Halley,
Antarctica based on frost-point hygrometer measurements”, Antarctic Sci. vol. 11, pp. 100 - 104, 1999.
[3] T. Ranta-aho, L. Stormbom,
“Real time measurement using the
warmed sensor head method”, in
Proc. 4th International Symposium
on Humidity and Moisture, ISHM,
pp. 583 - 588, 2002
[4] Makkonen, L., and Laakso,
T., “Humidity measurements in
cold and humid environments”,
Boundary-Layer Meteorology, vol.
116, Number 1, pp. 131-147(17),
2005.
[5] L. Makkonen, “Analysis of rotating
multicylinder data in measuring
cloud-droplet size and liquid water
content”, J. Atmos. Oceanic Tech-
169/2005
laboratory experiments [8] that,
in humid air between 0 and -20
ºC, supercooled dew may form
on the mirror rather than frost,
making the interpretation of the
measurements prone to errors.
Furthermore, the concept that
the temperature at the time of
nucleation on a cold surface necessarily corresponds to the equilibrium frost point has recently been shown to be questionable [9]. Thus, it appears that
Vaisala’s heated humidity probe
HMP243/HMT337 is more suitable for measurements in arctic
conditions than cooled-mirror
hygrometers. ●
nol. vol. 9, pp. 258 - 263, 1992.
[6] S. Mäkinen, “Labko Ice Detector
LID-2000”, in Proc. Boreas II
Meeting, pp. 196 - 202, 1994.
[7] Anon, CIMO Publication, WMONo. 807, World Meteorological
Organization, 1994.
[8] Anon, “ATD SHEBA ISFF FluxPAM project report, Appendix A:
Laboratory tests on RH measurement by capacitance sensors at
the frost point”, National Center
for Atmospheric Research, http://
www. atd.ucar.edu/rtf/projects/
sheba/ rh.lo.T.isff.html, 2002.
[9] B. Na, and R. L. Webb, “A fundamental understanding of factors
affecting frost nucleation”, Int. J.
Heat and Mass Transfer vol. 46, pp.
3797 - 3808, 2004.
Thomas Spieß and Jens Bange
Institute of Aerospace Systems
Technische Universität Braunschweig
Braunschweig, Germany
Vaisala INTERCAP® Humidity
and Temperature Probe HMP50
in Airborne Measurements
Figure 1: T200 aircraft
(Meteorological-Micro AerialVehicle, M²AV).
The Institute of Aerospace Systems provides, among other things, airborne measurement
systems for meteorological applications, field experiments, and atmospheric science. A brandnew system in this field is the M²AV (Meteorological-Micro Aerial-Vehicle). MAVs are aircraft
as small as birds, acting as airborne robots that fly completely autonomously using GPS and
pre-programmed waypoints.
T
he T200 aircraft (Figure 1)
of the “Carolo” MAV family is used for meteorological measurements. This is a twinpropeller aircraft with a wingspan
of 200 cm. It is hand-launched,
which makes handling and operating the aircraft very easy. The
maximum take-off weight is 4
kg, including 1500 g of payload.
The T200 is classified as a “model aircraft”, and is therefore less
subject to air-safety rules than a
heavier aircraft. The payload of
the M²AV includes meteorological probes, mounted in the noseboom (Figure 2) outside the influence of the propulsion. The
miniature 5-hole-probe is necessary for the determination of the
wind vector, which can be calculated from the airspeed, position,
and altitude of the aircraft.
Temperature and humidity are measured with the Vaisala INTERCAP® Humidity and
Temperature Probe HMP50.
The HMP50 is a very user-friendly probe. Thanks to the connections and fixings it can be replaced and integrated easily into the M²AV noseboom. Furthermore, the probe provides an amplified signal, which makes post
processing unnecessary. The data is of a very high quality. The
probe offers good long-term
stability and absolute accuracy
of measurements. The measuring range of the HMP50 also allows for measurements in polar
and tropical regions. It is also
lightweight, which is important
for the M²AV. An additional fast
temperature sensor provides turbulent fluctuations, while the on-
board 3D-GPS system gives the
M²AV’s accurate position, altitude and attitude. All measurements are stored on a standard
flash-card. After the flight, the
data is transferred with a cardreader and is ready for analysis.
Cost-effective airborne
turbulence probe
When developing the M²AV,
the goal was to achieve a costeffective airborne turbulence
probe. The energy transfer of
sensible heat from the surface
into the atmospheric boundary
layer can be determined with
the M²AV. It can be used to supplement other measurement systems (e.g. remote sensing, towers,
ground stations). Measurements
in remote areas and critical situations where manned flights
are too risky also become possible - e.g., over an active volcano
(performed in April 2005), in the
Arctic or Antarctica (scheduled
for December 2005), or even in
the polar night. The range of applications in clouds is presently
being investigated.
same level as that of the helicopter-borne turbulence probe Helipod (Figure 3), the M²AV offers a competitive alternative
due to its easy handling and versatility. Furthermore, the acquisition and maintenance costs are
very low compared to research
aircraft or other meteorological
instruments.
The Braunschweig Helipod
is also operated by the Institute
of Aerospace Systems. It, too,
benefits from Vaisala technology: the long-term stable humidity measurements are carried out
with a Vaisala HUMICAP® sensor. In the future we hope to perform supplementary M²AV measurements during Helipod campaigns to achieve better temporal and spatial coverage and resolution. ●
Figure 2: Meteorological probes
mounted in the noseboom of the
T200.
Further information:
www.m2av.de
M²AV versus helicopterborne turbulence
probes
In spite of their small size,
M²AVs carry out high-quality
turbulence measurements. Although the absolute measurement accuracy is not on the
Figure 3: The Braunschweig Helipod.
data quality
versatility
handling
acquisition cost
maintanance
Research aircraft
++
+
o
--
--
M²AV
o
o
++
+
+
169/2005
7
Timo Ranta-aho, Product Line Manager
Harri Lehtonen, Project Manager
Vaisala
Helsinki, Finland
Introducing Vaisala HUMICAP® Humidity and
Temperature Transmitter Series HMT100
New Flexibility in Demanding
HVAC Applications
Several different applications require reliable humidity measurement.
Stability rooms and chambers come in many sizes, all of which
require vigilant monitoring of temperature and humidity. The trend
in greenhouses is towards room-specific humidity sensors. Fruit
and vegetables are stored and ripened in specially built rooms that
contain systems for controlling humidity. Outside air measurements
are needed in weather reporting and forecasting but also in many
other applications, such as building automation.
T
he Vaisala HUMICAP®
Humidity and Temperature Transmitter Series
HMT100 has been introduced
for humidity and temperature
monitoring, especially in demanding HVAC (heating, ventilation and air conditioning) applications. Several optional features make it a flexible solution for the user, who can order
a transmitter that optimally fits
their specific application.
Reliable performance
in dusty and humid
environments
Alternative output
parameters and output
signals
The HMT100 can measure relative humidity or dewpoint alone,
or either one of these together
with temperature. Relative humidity is the most commonly
measured parameter, for example, when the effects of humidity
on storage, use and consistency
of materials and products need
to be monitored. On the other
hand, dewpoint provides a temperature-independent humidity
parameter such as when incoming air is supplied into an air conditioning network or the temperature where condensation would
occur needs to be known.
Different controllers and
peripherals work using various types of input signals. The
HMT100 outputs the measurement results as either a loop pow-
169/2005
to re-adjust the HMT100 transmitter at the measurement site.
The probe can easily be changed
to another HMP100 probe,
which is either supplied directly from the factory or calibrated elsewhere. Alternatively, the
transmitter can be adjusted using
a system such as the Vaisala HUMICAP® Hand-Held Humidity
and Temperature Meter HM70
and a suitable connection cable.
The HM70’s indicator shows the
readings of both the HMT100
and the reference probe simultaneously, and the adjustment can
be made quickly and easily.
The HMT100 can also be
calibrated in a conventional way
using the Vaisala Humidity Calibrator HMK15, or by sending the unit to a Vaisala service
center.
ered 4...20 mA signal or as a linear voltage signal.
Choice of probes and
displays
The HMT100 comes with either a fixed humidity probe for
mounting the unit on a wall or
with a cable probe that enables
the probe to be installed at a distance from the transmitter body.
A separate duct installation kit
enables the probe to be installed
in an air channel, where the exact
installation depth of the probe
can be adjusted. Three different
cable lengths are available and a
separate extension cable allows a
maximum 20 m distance between
the probe and the transmitter.
The HMT100 can also be or-
dered with a local LCD display
which instantly shows the user
the observed humidity and temperature levels.
Interchangeable probe flexibility in calibration
As a new feature, the HMT100
series incorporates a model with
an interchangeable probe. This
probe can also be bought separately as a spare unit for the
HMT100 transmitter. When adjusting the transmitter, the adjustment result is stored in the
HMP100 probe. The probe can
therefore be adjusted in a calibration laboratory using another HMT100 body.
The interchangeable probe
provides the user with a new way
The transmitter cover is dust
and water spray resistant and
meets the IP65 requirements.
This makes the HMT100 particularly suitable for wet and humid environments that are regularly cleaned with sprayed water. A separate weather shield
and a radiation shield are available for installing the HMT100
outdoors. In addition, the sensor
elements can be protected either
with a plastic grid, with a membrane filter, or with a durable sintered filter.
The HMT100 incorporates
the Vaisala HUMICAP® sensor,
which has excellent stability and
is insensitive to dust, particulate
dirt and most chemicals. ●
Marikka Metso
Editor-in-Chief
Vaisala
Helsinki, Finland
Artist’s conception of
Cassini approaching
Saturn. (Courtesy
NASA/JPL-Caltech)
Update on the CassiniHuygens Mission
In Vaisala News 167 we reported on the Cassini-Huygens
space mission that set out to explore planet Saturn and
the largest of its known moons, Titan. The mission has
two distinct elements: the Cassini orbiter and the onboard
Huygens probe. Released from Cassini, the Huygens probe
successfully landed on Titan in January 2005. It carried eight
Vaisala BAROCAP® barometric pressure sensors on board as
part of one of its six science instruments.
S
aturn is the second largest planet in our solar system, after Jupiter. It is
a gaseous planet with an atmosphere comprising mostly of hydrogen and helium. The bright
rings for which Saturn is best
known are comprised of ice and
rock particles.
Saturn has more moons than
any other planet known to us.
The largest of them is the aptly named Titan, discovered by
Dutch scientist Christiaan Huygens in 1655. Saturn itself was
first spotted by Italian astronomer Galileo in 1609. Since then,
its mysteries have fascinated scientists worldwide.
To shed light on the conditions on and around the sixth
planet from the Sun, a spacecraft
was constructed in a joint effort by NASA, the Italian Space
Agency (ASI), the European
Space Agency (ESA), as well as
numerous scientists worldwide.
The Cassini-Huygens spacecraft was launched on October
15, 1997 from Cape Canaveral in
Florida, USA.
After years of traveling
through space, and borrowing
gravitational energy from other
planets to speed it on its way, the
Cassini-Huygens spacecraft entered the Saturn system on July 1, 2004. This marked the start
of its 4-year mission. The Cassi-
ni orbiter will carry out a total of
75 orbits around Saturn. It will
also make repeated close flybys
of Titan.
Exploring Titan
Titan is a captivating object of
study, as it exhibits many similarities to conditions that may well
have once prevailed on Earth. It
has a nitrogen-rich atmosphere
like Earth, and although most
agree that its surface tempera-
169/2005
Huygens probe landing on
Titan’s surface, artist’s rendition
(Courtesy NASA/JPL-Caltech)
ture (-181 °C) is too hostile for
the development of life, there are
also those who do not exclude
the possibility of some life forms
existing on Titan.
On December 25, 2004, the
Huygens probe separated from
the Cassini spacecraft for its 20
day journey to Titan. It successfully entered Titan’s upper atmosphere on January 14, 2005,
and descended with three sets
of parachutes to its surface. The
descent phase lasted around 2
hours 27 minutes with a further
1 hour 10 minutes on the surface.
The mission was a complete success. Obtaining surface data
was more than many had dared
to hope for since there were no
guarantees that the probe would
survive the landing. Huygens
made history by being the first
spacecraft to land on a moon in
the outer solar system.
HASI: Huygens
Atmosphere Structure
Instrument
The Huygens probe carried six
science instruments to sample
10 169/2005
Titan’s atmosphere and surface
properties. Throughout the mission, data was collected from all
instruments. One of these was
the Huygens Atmosphere Structure Instrument (HASI) - a multisensor package designed to measure the physical properties of Titan’s atmosphere. Its task was to
measure the temperature, pressure, turbulence, and the atmospheric conductivity, as well as to
search for lightning.
HASI’s sensor package devoted to atmospheric pressure
measurement - the Pressure Profile Instrument (PPI) developed
by the Finnish Meteorological
Institute - contained eight Vaisala BAROCAP® barometric pressure sensors. BAROCAP® is a
capacitive absolute pressure device manufactured by silicon micro-machining. When pressure
changes, the silicon diaphragm
bends and changes the height
of the vacuum gap in the sensor.
This alters the sensor’s capacitance, which is measured and
converted into a pressure reading. The Vaisala BAROCAP® is
known for its excellent hysteresis
and repeatability characteristics
as well as its outstanding temperature and long-term stability.
The mission continues
As data from the Huygens probe
is being analyzed, the story of
Titan gradually starts to unfold.
For instance, we now know that
Earth-like processes of tectonics, erosion, winds, and perhaps
volcanism, shape Titan’s surface.
However, the work has only just
begun - there’s enough data to
keep Huygens scientists busy for
a long time yet.
Although the Huygens mission has been successfully completed, the Cassini spacecraft
will continue its orbits until June
2008 - providing scientists with
vital data and the best views ever
of this fascinating, vast region of
our solar system. ●
Sources:
ESA/NASA/JPL
Peter Eriksson
Account Director
Vaisala
Paris, France
DORIS - Doppler Orbitography
and Radiopositioning
Integrated by Satellite
DORIS is a Doppler satellite tracking system developed for
precise orbit determination and precise ground location.
T
he DORIS system, designed and developed by
the CNES (the French
Space Agency), in collaboration
with GRGS (Space Geodesy Research Group) and IGN (French
Geographic Institute), has a dual purpose.
This dual capability has enabled DORIS to be used in numerous applications since 1990.
The system is used in ocean or
ice field altimetry missions such
as Topex/Poseidon, studies of
the shape and movements of the
Earth, as well as many location
services where different satellites are equipped with the DORIS receiver. Operational since
the launch of the remote sensing satellite SPOT-2, this system
is used to determine the position
of the satellite to within 10 cm
in realtime, and about 1 cm after ground processing. The sys-
tem also measures and calculates
the ionospheric correction. Accurate knowledge of satellites’
orbits is essential for altimetry
missions that measure sea level.
This monitoring of the oceans is
a major objective for the scientific community. Rises in sea level due to the potential effects of
global warming could have disastrous consequences for many areas in the world.
Reference point
stations
To be able to accomplish these
measurements, the DORIS system is using a network of about
60 ground stations as reference
points on Earth. Each of these reference point stations is equipped
with the Vaisala Combined Pressure, Humidity and Temperature
Transmitter PTU200, providing
accurate local reference data on
Vaisala Combined Pressure, Humidity and Temperature Transmitter
PTU200.
all of these parameters at the installation site. On the satellite, an
antenna pointed towards Earth
receives radio waves emitted by
ground stations in the DORIS
network. An electronic receiver measures the frequency shift
caused by the Doppler effect.
During 2000-2002, Vaisala
has delivered approximately 70
PTU200 transmitters to the Toulouse-based company S.M.P., a
major international provider of
satellite communication systems,
data transmission, data processing (Telecommand, Telemetry and
control) and microwave products.
S.M.P. has integrated the transmitters into their own aforementioned reference stations.
Three-in-one
measurement
which combines three measurement parameters: pressure, temperature and humidity. The applications of the PTU200 range
from calibration laboratory environmental condition monitoring, to laser interferometer active wavelength compensation,
and GPS meteorological measurements. The PTU200 transmitters are available with one or
two pressure transducers. Three
different kinds of sensor heads
can be used with the PTU200.
The transmitters use a RS232 or
RS485 serial interface and they
are also available with a local display. In outdoor applications, it
is recommended to use the PTU200MIK Outdoor Installation
Kit. In addition, a mounting tripod is available for temporary
field installations. ●
The PTU200 transmitter is a mature, well field-proven product,
The DORIS system.
169/2005 11
Isao Naito
Sales Group Manager
Shigeki Shimizu
Met Sales Manager, Japan & Korea
Vaisala
Tokyo, Japan
Japan Meteorological Agency Adopts
Vaisala Barometers
Vaisala has been a trusted supplier to the Japanese market for years.
One of its long-standing partners is the Japan Meteorological Agency
(JMA). Recently a decision was made to adopt the Vaisala BAROCAP®
Digital Barometer PTB220 in a portable oak case as the JMA roundcheck standard (reference) barometer.
T
he selection process for the
various instruments used
in the JMA surface weather observation system started
several years before their actual
adoption. Various comparative
tests were conducted over a period of time with barometers of
several makes.
Following the tests, JMA
evaluated potential products,
achievements in the market, prices, future potential, and manufacturer’s support systems. The Vaisala BAROCAP® Digital Barometer PTB200AD (later replaced by
PTB220) was selected through
cooperation with partners Sanko
Tsusho Co., Ltd. and system integrator Meisei Electric Co. Ltd.
JMA has 57 weather stations
and 99 meteorological observato-
ries in Japan, some of which are
operated unmanned. The highly reliable Vaisala 3-sensor type
PTB220 series is a good match
with JMA’s automation program.
Replacing the old
mercury barometer
JMA had used a mercury barometer as the reference barometer
for over 130 years, from the beginning of its history. However, measurement with a mercury
barometer is a troublesome task.
Temperature and gravity values
in particular need compensation
that requires skill and experience
in handling as well as in reading
the values. Because of the toxic nature of mercury in volume,
transportation and installation is
a genuine burden. Due to these
Vaisala BAROCAP® Digital Barometer PTB220TS in a portable oak case.
factors, there was a demand at
JMA for a round-check reference barometer that is easier to
handle.
JMA’ s advanced study found
that the Vaisala BAROCAP®
Digital Barometer PTB220TS in
an oak case has a wealth of benefits, including its compact size,
durability and ability to indicate
the barometric value directly.
Data continuity and equipment
reliability are the most important
features of a reference barometer for JMA. To investigate the
long-term reliability and periodical maintenance requirements of
the PTB220TS barometer, JMA
carried out comparative readings
of barometric pressure together
with the old mercury barometer for over twelve months. They
found that the fluctuation of the
PTB220TS stayed within the
±0.15hPa range and showed no
trend of shifting to either side.
Vigorous
performance-testing
An air piston pressure gauge was
used as the reference meter. Ac-
12 169/2005
From left: Yasuhiko Sato,
President, Sanko Tsusho Co., Ltd.,
and Isao Naito
curacy confirmation tests included instrumental difference, temperature, vibration, long-term
stability and durability/safety
for transportation. JMA checked
and compared the digital barometers with the mercury barometer once a week and applied compensation if necessary. The result
of the comparison of all 64 digital barometers during 1995-1998
indicated that the shortest period of offset value fluctuation
within ±0.4hpa was 14 months.
Therefore the period of reading
comparison with the then barometer was set at one year. Due
to the good results, JMA decided to adopt the Vaisala digital barometer by 2003, and it has been
in active operation since 2004. ●
Long-term stability
Comparative tests for approximately 1 year
Temperature characteristics test
Constant temperature chamber tests with -20, 0, 30,
50 degrees Celsius.
Absolute pressure test
Station pressure tests with 5 different points of 880,
920, 980, 1000, 1040 hPa for comparison of increasing and decreasing pressure, and hysteresis.
Accelerated stability test
Reducing the test pressure to about 3hPa lower
than the station pressure and resuming normal
pressure at 5-minute intervals, until an equivalent
of 700 days of operation is reached.
Vibration test
Amplitude: ±2mm, test frequency: 300rpm
Maria Uusimaa
Application Manager
Vaisala
Helsinki, Finland
Studying the Changing
Climate in Controlled
Environment Chambers
The University of Sheffield can be proud of their controlled
environment facilities. The Department of Animal and
Plant Sciences houses a total of 58 state-of-the-art
controlled environment chambers and rooms for plant
growth studies, which can simulate any climate from the
arctic to the tropics.
T
he University of Sheffield
recently celebrated its hundredth anniversary. Founded in 1905, the history of the university stretches back to the early
19th century, when the Sheffield
School of Medicine was founded in 1828. Today, the university consists of 70 academic departments, and has over 24,000
students.
The Department of Animal
and Plant Sciences has a strong
reputation in the research it conducts, especially in plant science,
zoology, and microbial ecology.
Also remarkable are its facilities
for plant growth studies - a controlled environment facility of
chambers and rooms for studying how plants from all over the
Earth and from various ecosystems respond to climate changes.
169/2005 13
Darren Rose is the Laboratory Superintendent at the Department of
Animal and Plant Sciences, University of Sheffield.
Controlling the
Environment
Although the plant growth chambers of the University of Sheffield are housed within the Department of Animal and Plant
Sciences, other departments,
such as the Department of Molecular Biology and Biotechnology also make use of the state-ofthe-art chambers.
The floor areas of the largest
walk-in chambers are over 15 m2
in size. The chambers are computer controlled and monitor
temperature, humidity, photosynthetically active radiation, as
well as carbon dioxide concentration. The chambers measure
humidity and CO2 with Vaisala
products. The most recent chambers are equipped with the Vaisala CARBOCAP® Carbon Dioxide Probes GMP343. “We are al-
14 169/2005
so going to use the Vaisala probes
in all our new projects”, says
Darren Rose, Laboratory Superintendent of the department.
Temperatures in the controlled environments can range
from summer to winter, humidity from dry tundra to a tropical
rainforest, and the CO2 concentration from ambient to an elevated CO2 concentration of up
to 2000 ppm. A current development is to extend the CO2 control range of a number of chambers to sub-ambient levels of
180ppm up to elevated concentrations of 4000ppm, regardless of the outside ambient CO2
concentration, which is typically
around 380ppm.
Looking into the future
The chambers at the University of Sheffield can simulate any
environment on Earth. The research conducted in the chambers aims to determine the consequences of climate and atmospheric change on plants.
Since it is fairly evident that
the atmospheric CO2 concentration will increase in the future,
the impact of elevated CO2 concentration on Earth’s vegetation
and the way in which current
ecosystems will be altered needs
to be studied. The atmospheric CO2 concentration, the global vegetation distribution and its
structure, as well as the current
climate are linked in an extremely complex manner. Changes in
any of these areas affect the entire terrestrial carbon cycles between the atmosphere and the
biosphere.
It is also important for food
production to understand the
consequences of climate change
on crop growth. A changing climate will also have an impact on
the number and species of pests
and diseases capable of devastating the crops. The more experimental studies are conducted in
the plant growth chambers, the
more accurate models of likely
future climate scenarios can be
constructed.
In addition to studying future changes in the climate, the
controlled environments will also simulate past climatic events.
For example, a polar environment with a sub-ambient CO2
concentration simulating a prehistoric ice age can
soon be set up by
simply pressing
a few buttons.
Simulating a
past climate
helps the researchers to understand the effect
of climate change on
plant evolution.
Chamber calibrations
The frequent use and high standards required from the chambers means they need to be serviced at least every 6 months.
“We have a very strict calibration
procedure”, says Darren Rose,
who as a Laboratory Superintendent ensures that everything runs
smoothly at the facility. A calibration set comprising the Vaisala HUMICAP® Hand-Held Humidity and Temperature Meter
HM70 and a Vaisala CARBOCAP® Carbon Dioxide Probe
GMP343 is in frequent use for
the chamber field-checks.
Plans for expansion
The Department of Animal and
Plant Sciences is planning to
expand its impressive facilities
by building two research glasshouses and a polar simulation research growth-room. The new facilities will add some 500 m2 to
the controlled environment area and provide the possibility
to control and monitor temperature, humidity, light, and CO2
concentration. ●
Vaisala CARBOCAP® Carbon
Dioxide Probe GMP343.
Norikazu Eguchi
Graduate School of Environmental Science
Hokkaido University
Takayoshi Koike
Professor
Hokkaido University, FSC
Sapporo, Japan
Tatsushiro Ueda
Technical Engineer
Hokkaido DALTON Co.
CO2 Fumigation System for the Prediction of the State of Forests in the Future:
Free Air CO2 Enrichment
Experiment in Northern Japan
Atmospheric CO2 concentration is about 350-400 parts per million by volume (ppmv) at
present, but it is predicted to increase up to 540-970ppmv by the end of the 21st century. Will
the carbon fixation capacity of trees and forests change in the future? What is the fate of
our forests in a world with an increased atmospheric CO2 concentration? The Free Air CO2
Enrichment (FACE) experiment hopes to provide some answers to these questions.
A
fter Japan's ratification
of the Kyoto protocol
for moderating the increase of CO2 in the atmosphere,
we have speculated on the role
of forest ecosystems in CO2 uptake. To be able to evaluate the
carbon balance of the atmosphere in the future, we urgently need to understand how forests or trees respond to the predicted high CO2 environment.
Many studies have investigated
forests under elevated CO2 and
temperature conditions, simulating the global greenhouse effect. In Sapporo, Japan, we have
established a small-scale Free
Air CO2 Enrichment (FACE)
experiment, using the Vaisala
CARBOCAP® Carbon Dioxide
Probe GMP343.
Beyond earlier
CO2 enrichment
experiments
oped. The FACE structure and
the control system for CO2 concentration is shown in Figure 1.
Wind direction is detected with
an anemoscope. The CO2 sensor
positioned at the center of FACE
Figure 2: The Vaisala
CARBOCAP® Carbon Dioxide
Probe GMP343 inside the FACE.
During the early stages of the
experiments, a closed chamber
or open-top chamber (OTC)
was used to regulate the CO2
concentration. Unfortunately, since the conditions inside
these chambers were otherwise
quite different from the natural environment (e.g. in terms
of temperature, moisture, light,
and wind speed), it was ambiguous to apply the results directly to natural conditions. This is
why the FACE system was devel-
Figure 1: Structure of the FACE system
169/2005 15
550 ppmV
450 ppmV
Figure 3: Daily variation of CO2 concentration inside the FACE (August 25, 2004).
can regulate the rate of CO2 gas
released upwind from the hole
in the tube and sustain the target
CO2 concentration.
The setting
The FACE system that we have
constructed is located in the Sapporo Experimental Forest, Field
Science Center for Northern Biosphere (FSC), Hokkaido University, in northern Japan (43˚06’N,
141˚20’E). It was designed and
constructed by Mr. Tatsushiro Ueda, Technical Engineer at
Hokkaido DALTON Co., under the supervision of Professor
Takayoshi Koike from Hokkaido
University. The system is based
on the alpine FACE system of the
Swiss Federal Institute of Technology (ETH, Zürich) and the
University of Basel in Switzerland. The Hokkaido FACE system was completed in the spring
of 2003. There are three five-meter high circular plots with a diameter of six meters each, that
are maintained at elevated CO2
levels. Three plots of six-meter
diameter constitute a control
group with ambient CO2 levels.
This is the first study for woody
plants in Asia and it simulates
the early stages of forest succession. Eleven kinds of deciduous
tree saplings native to the cooltemperate region in Japan were
used. These tree species are alder,
two types of birch (white birch,
Monarch birch), larch (early successional), basswood, kalopanax,
Manchurian ash, elm (mid successional), maple, beech, and oak
(late successional).
The target CO2 concen-
16 169/2005
tration of the FACE system is
aimed at 500 ppmv during daytime, which has been estimated
to be the average level of atmospheric CO2 in 2040. To control
the CO2 concentration, we introduced the Vaisala CARBOCAP®
Carbon Dioxide Probe GMP343
(Figure 2). The accurate probe
type of CO2 sensor enables a
well-regulated experiment. The
CO2 gas was supplied with a special tubing system used for irrigation in Australia. The tube has a
knot at one-meter intervals for
balanced CO2 pressure, which
helps in creating a uniform supply of CO2 to the target space in
FACE. The result of CO2 concentration control is shown in
Figure 3. The proportion of daytime (from 4:00 am to 7:00 pm)
within the 500±50ppmv parameter was 95.02%, which is a very
high accuracy.
The findings
We are now obtaining interesting
results from our two-year FACE
experiment. Under elevated CO2
concentrations, the leaf stomata (the microscopic pores under
the leaves, which open outside
to give out oxygen and water vapor and take in CO2) tended to
close and the transpiration rate
decreased in almost all tree species grown on both volcanic ash
soil and brown forest soil. However, the photosynthetic rate of
most species tended to increase.
Consequently, the water use efficiency of leaves increased significantly. These results indicate that,
under elevated CO2 concentrations, the saplings would be able
to keep up a high photosynthesis
rate even in dry conditions.
In the second year of the experiment, photosynthetic downregulation (maximum photosynthetic rate at light and CO2 saturation showed lower values in
high CO2 grown tree saplings
than in ambient CO2 grown
ones) was found in white birch
but not in alder. The amount of
photosynthesis enzyme (Rubisco) in white birch at high CO2
was lower with an extra-accumulation of starch in the chloroplasts than at ambient level
CO2. Contrary to white birch,
no down-regulation was found
in alder. Because of the symbiosis with actinomycete Frankia
sp. - a large carbon sink and resource for nitrogen - alder could
maintain a high photosynthetic
rate. However, herbivore (plant
eating animals, in this case mainly the leaf beetle; Agelastica coerulea) attacked its leaves, and
most of the alder saplings died
on volcanic ash soil which is poor
in nutrients. Under infertile soil
conditions, the photosynthetic capacity of alder would be accelerated by high CO2 concentrations, accompanied by an increase in Frankia sp., which may
supply nitrogen to alder as a host
plant. Alder leaves with high nitrogen levels attract herbivores.
These plant-insect interactions
are also being studied in the
FACE experiment.
With our experiment, we aim
to understand the physiological
and ecological traits of trees and
forests in a CO2 enriched world.
Ultimately, we hope to accurately predict the carbon fixation capacity of forests in the future. ●
From left: T. Ueda, T. Koike, N. Eguchi, K. Karatsu, N. Morii, N.
Ishida and T. Hida in front of a FACE plot.
Maria Uusimaa
Application Manager
Vaisala
Helsinki, Finland
AGA is part of the Linde Group, which is the
leading gas producer in Europe and the fourth
largest gas producer in the world.
Safety First in CO2 Production
Since excess carbon dioxide in our
surroundings replaces the vital oxygen,
carbon dioxide needs to be monitored in all
places where it is produced, stored, shipped,
or used. The AGA CO2 production plant
recognizes this fact and has been monitoring
their indoor CO2 levels since the facility
opened in 1991. AGA’s safety alarm system
integrates the Vaisala CARBOCAP® Carbon
Dioxide Modules GMM221.
T
he AGA corporation in
Finland is part of the
Linde Group, the leading
gas producer in Europe and the
fourth largest gas producer in
the world. AGA’s main gas products are oxygen, nitrogen and argon, which together generate half
of the company’s revenue. These
so-called air gases are produced
by distilling air in very low, cryogenic temperatures. In addition
to the air gases, other important
AGA products include hydrogen
and carbon dioxide.
The Kilpilahti process
industry cluster
AGA’s carbon dioxide production plant is located in a very se-
cure facility inside a Neste Oil
refinery in Kilpilahti near Porvoo, Finland. The Kilpilahti area is situated roughly 35 kilometers east of Helsinki, and is the
biggest process industry cluster in Northern Europe. The area has its own power plant and
harbor. The Kilpilahti industry
cluster covers 13 square kilometers and employs over 3500 people. Since many noxious and inflammable products are handled
in the area, it is vital that safety issues are taken very seriously. Each of the 3500 employees
has passed a safety and security
test in order to acquire a permit
to work in Kilpilahti.
In addition to the Neste Oil
169/2005 17
refinery, a broad range of other
petrochemical companies and
supporting companies operate
in the Kilpilahti area. AGA operates in the area both inside and
outside the actual oil refinery.
Atmospheric gases are manufactured in an air separation plant,
whereas CO2 is produced next
to a Neste Oil hydrogen reformer
at the very heart of the refinery.
CO2 has many uses
AGA and Neste Oil operate side
by side at the refinery. Neste
Oil uses methane in its reformer to produce the hydrogen. Carbon monoxide is formed as a byproduct. A converter is used to
transform the carbon monoxide and water into carbon dioxide. The crude carbon dioxide
needs to be washed, pressurized,
distilled, and cooled to become
commercially sold carbon dioxide. This is the responsibility of
the AGA CO2 production facility. The resulting end product
is pressurized high-purity CO2,
which is ready for any commercial use. The hydrogen reformer and the carbon dioxide production plant are in operation 24
hours a day and over 8000 hours
annually, resulting in almost constant operation except for short
maintenance breaks.
The carbon dioxide produced at the Kilpilahti production plant has several uses. For
example, greenhouse farmers
use it to fertilize their crop. The
food industry uses the high purity substance as a protective gas
in food packaging and the beverage industry for the bubbles in
soft drinks. Carbon dioxide is also used as a refrigerant and the
paper industry uses CO2 to produce bicarbonate of soda used
in pulp production. AGA also
processes a part of the gaseous
carbon dioxide into a solid dry
ice. Dry ice is the solid form of
carbon dioxide, which melts at 79°C and directly sublimates into gaseous carbon dioxide. It is
commonly used for cooling and
refrigeration purposes, for example in the food industry.
18 169/2005
Investing in safety
Safety is of the utmost importance around the whole Kilpilahti area and AGA’s CO2 production plant is no exception.
The safety system design of the
plant has been made in co-operation with a company specializing in gas monitoring systems. At
the heart of the safety alarm system are the CO2 sensors. AGA
selected infra-red gas transmitters based on the Vaisala CARBOCAP® Carbon Dioxide Modules GMM221.
“Typically the CO2 concentration here is less than 1000
ppm, which is a very good indoor air quality. Rising levels are
constantly monitored with the
Vaisala sensors. We have been
extremely happy with their operation”, says Hannu Rimaila of
AGA, who is in charge of instrumentation and automation at the
liquid production and process
plants.
The carbon dioxide sensors at the AGA CO2 production plant are monitoring the environment in all occupied spaces. The transmitters are placed
at head level, since CO2 is heavier than air and first accumulates near floor level. As a supplement and for early detection
of rising CO2 levels, the sensors
have been placed close to potential leakage points, such as pipelines and valves.
The number of transmitters
required in the monitored area depends upon the ventilation
system and air flow. At the AGA
carbon dioxide production plant,
there is a total of ten CO2 transmitters monitoring the area. Although no leakages have ever
occurred, the risk remains and
therefore the CO2 levels are constantly monitored.
Future plans
The future will bring changes
to carbon dioxide production
at Kilpilahti. Neste Oil will be
building a new hydrogen reformer and to ensure that their cooperation continues, AGA will also be constructing a new CO2
Hannu Rimaila is in charge of instrumentation and automation at the
AGA liquid production and process plants.
manufacturing plant adjacent to
the reformer. The new plant will
be fully operational by 2007. Because of the good experiences
from the old plant, the new plant
will also be equipped with CO2
monitoring equipment from
Vaisala. Once the new plant is
operating at full capacity in 2007,
the CO2 production of AGA in
Kilpilahti will increase to the extent of being able to cater for
CO2 requirements throughout
the entire Baltic Sea region.
Although CO2 is produced
as a by-product of many combustion, brewing, and fermentation processes, it is very difficult
to collect efficiently from these
small sources. For example, the
CO2 concentration in combustion gas is often very low for efficient recovery and the gas itself
contain impurities such as sul-
phur and nitrogen compounds,
which may be difficult to remove.
The proximity of a large source
of high concentration CO2 in
Kilpilahti allows AGA to utilize
the waste from the hydrogen reformer for a commercial product. Globally, these types of CO2
manufacturing facilities are very
often found next to oil refineries,
chemical or petrochemical process facilities. ●
Dr. Michel Rosengaus Moshinsky
Head of the Unit
National Meteorological Service/SMN
National Water Commission
Mexico
Lauri Tuomaala
Product Line Manager
and
Hannu Kokko
Product Manager
Vaisala
Helsinki, Finland
Modernizing Weather
Information Networks in
Mexico
This article describes the measurement problems experienced at the National
Meteorological Service (Servicio Meteorológico Nacional) of the National Water
Commission of Mexico and how they can be solved utilizing the Vaisala Weather
Transmitter WXT510, together with PDAs and some additional hardware. We
also introduce another, more advanced solution - the Vaisala HydroMet™
Automatic Weather Station MAWS100, which incorporates the Vaisala Weather
Transmitter WXT510.
V
aisala introduced the
Vaisala Weather Transmitter WXT510 into the
global market in October 2004.
The WXT510’s various interface
options means that it can be easily integrated with data loggers,
PDAs or machine to machine
communication modules. It is especially suitable for dense measurement networks.
Case: National
Meteorological Service
of Mexico
The network of traditional climate stations (TCS’s) in Mexico is a major source of climatological information in the country. Many governmental and private decisions are taken on the
basis of data coming from these
stations, e.g. identification of normal weather conditions, evaluation of potential extreme occurrences, daily follow-up of the water cycle, objective identification
of draught conditions, adjustments to electricity fees, design
of works and systems, etc. This
Dr. Rosengaus verifying every
detail of the tailored cut model.
is the data that is most frequently
requested from Mexico’s National Meteorological Service (SMN).
Presently, there are 3,200 stations in operation, with an average distance of 20 km between
them. The maximum number
of stations operating simultaneously was reached in 1980-1985,
with approximately 4,200 stations. A human observer reads
the results once a day (at 8:00
a.m., local time) and writes them
down in a paper record. A subset of 900 stations are linked by
radio or telephone and, apart
from generating the paper records described above, these
stations transmit their measurements once a day to a concentration point where they are captured and entered into a database. Paper records, once digitally captured, are sent to the
SMN to be entered into the national weather database, which is
currently managed through the
WMO’s CLICOM system. As of
December 31st 2004, the historical database had 12’440,747 re-
cords, where one record represents one month (28 to 31 values)
of one of the nine variables for
one station.
Problems with the old
network
The TCS network has considerable limitations:
• It does not provide practically
any information about the diurnal cycle. There is a lack of
proportion between the cost
of operating the network and
the quality of data obtained.
The trips (ideally monthly)
to collect data are very costly, while the amount of data
collected at each site is very
limited.
• Timeliness of data is poor.
Except for the data coming
from the subset of stations
that report daily, data availability takes months (at times,
even years) after this has been
collected.
• Quality control is limited, especially because of the difficulty of managing a set of human operators, who are quasivolunteers, broadly distributed across the country.
169/2005 19
Vaisala Weather Transmitter
WXT510.
• Operations in the stations are
irregular, resulting in discontinuous records, a porous database and geographic density
that is inconsistent in time.
• Some important variables (basically humidity and wind) are
not measured.
After the introduction of the
Vaisala Weather Transmitter
WXT510, Mexico’s SMN immediately identified that this kind
of equipment could be the milestone of modernization for the
network of climate stations in
the country, providing several
different options. To begin with,
there is the possibility of recovering 1,000 stations whose operation had been lost since 19801985, at affordable prices. To
this end, a pilot test commenced
with 30 units operating for one
year. Rossbach de México, Vaisala’s exclusive representative in
the country, is a key partner in
this project.
The new station
configuration
The subset of instruments consists of five modern sensors in
a very compact package, similar in size to a coffee can: ultrasonic wind sensor (speed and direction), piezo electrical RAINCAP® sensor (accumulated rainfall, rain intensity and duration),
temperature, humidity and at-
20 169/2005
mospheric pressure - all protected from solar radiation but having an adequate flow of air from
the ambient environment. The
WXT510 is an intelligent multisensor that communicates with a
data recorder through its serial
interface. Individual characteristics of the instruments are excellent, certainly better than those
of traditional instruments presently used in TCS’s. Also, energy consumption is low enough
to consider an autonomous installation, far from commercial
electricity sources. Another important factor is that the package
has no mobile parts.
The entire station does not
attract attention to its state-ofthe-art technology when installed within a traditional weather station. The concrete foundation is 60 cm deep, and weighs
approximately 180 kg, which
makes it very difficult to extract
and move. The corrosion resistant mast, embedded in concrete,
is installed from the beginning
with a notch in the upper part,
oriented in such a way that if the
package of sensors has to be reinstalled, it is already properly oriented, which is essential for detecting the direction of the wind.
There is a no-cups anemometer,
an element which has historically been the object of vandalism.
Another popular target, the solar panel, is not evident at a distance because it is attached to the
upper part of the weather-proof
box (on the mast, above the upper edge of the railings). External
cables are not evident, nor is the
internal electronic instrument
visible. It is quite stable, not only
against the wind but also against
operators that may lean against
the mast. The wind sensor is not
subject to down wind trails from
any other component of the traditional weather station.
There are no exterior nuts or
bolts. It may only be disassembled with the access key. Even after cutting metal clamps on the
mast, the box is not totally removed, because it has additional
bolts at the center of the mast.
The data recording device is
a palm computer running Windows CE. Batteries are found behind the metal plate that appears
to be the background. Bolts to
detach the whole box are also
behind the plate. Normally the
screen displays the last measurements taken for the benefit of the
station’s operator. When dealing
with a station that reports daily,
this data is transmitted by telephone or radio. By pressing one of
the buttons, the operator is asked
whether data should be downloaded to the removable memory card. It is enough to do this,
extract the card, replace it with a
blank card, take the said card to
the data concentrating center and
- using a simple computer with the
proper card reader - copy the information to the hard disc.
The file is in ASCII text format. Therefore, while traditionally a visit to the station was to
collect paper records, now memory cards will also be collected,
regional data will be concentrated and sent via electronic means
to central offices and entered into the corresponding databases.
It is not necessary to shut down
the equipment in the weather
station in order to change cards
and indeed, it does not interrupt
measurement taking during that
time. The person collecting the
data does not have to do anything special to produce a continuous long term record because it is easy to link together
the text files of two consecutive
collection trips; the moment that
the last data transfer to the removable memory card occurred
is automatically marked. The data file has an identifier to avoid
any confusion in case the cards
from several stations are mixed,
even if they do not have an outside identifier.
The pilot test
The pilot test, planned as the operation of 30 multi-sensors for a
whole year (January 1st to December 31st 2005) under 100%
operational conditions, is necessary because this is the first time
that such equipment is used, except for internal tests carried out
by the manufacturer. Before investing large amounts of money in a true modernization of
the network of weather stations,
there must be evidence of the
correct operation of the instruments and the data collecting and
concentrating system, as well as
durability of the devices, and incidence of vandalism, etc. Moreover, the pilot test will allow for
necessary modifications before
starting a massive modernization
program. A relatively small area
close to the Valley of Mexico was
chosen as the test site, to enable
the specialized personnel from
the SMN to perform close monitoring tasks. As of December 1st
2004, 100% of the stations were
already installed and the personnel fully trained.
Since they are co-located
with 30 TCS’s presently operating, instantaneous (08:00), maximum and minimum temperatures as well as rainfall may be
checked against traditional instruments. This is particularly important in the case of rainfall because of the revolutionary measuring device (impact drum).
New possibilities
The system is likely to improve
the reliability of climatological
measurements in Mexico, significantly improve its temporal resolution and even open the possibility to recover points of measurement that have been lost in
recent years. It will also allow
for humidity, wind and pressure
measurements with adequate
density on Mexico’s geography.
The results of this pilot program for modernization will be
available not only for Mexico’s
National Water Commission
(CNA), but for similar efforts
in developing countries in Central America and the Caribbean
(WMO’s RA-IV), South America (WMO’s RA-III) and other interested nations. We are thankful to all who have helped us in
this significant modernization
project. ●
Left: Data recording device.
Right: Inside the weather-proof box.
VaisalaHydroMet™AutomaticWeather
StationMAWS100Incorporatingthe
VaisalaWeatherTransmitterWXT510.
Together with the Vaisala Weather Transmitter WXT510, the
Vaisala HydroMet™ Automatic Weather Station MAWS100
MAWS100
extends the field-proven quality and reliability of the Vaisala HydroMet systems to new applications. The MAWS100 is
a compact system for hydrometeorological monitoring when
a small number of sensors is required. It brings data logging,
in-situ calculations and data quality control, additional sensor interfaces, cellular telemetry and versatile powering options to the system incorporating the WXT510.
Sensors
The basic sensor suite measures wind speed and direction,
pressure, temperature, relative humidity and precipitation.
Optional sensors can be added to measure water level, soil/
water temperature, global and net solar radiation, for example. Generic and configurable 16 bit A/D conversions are
also provided in case the user wants to interface to their
own sensors. The high accuracy of meteorological data is
ensured by factory calibrated A/D conversion and advanced
data quality control and validation software.
Power
The MAWS100 is a low power device. The basic system is powered using mains power or a small 6 W/6 VDC solar panel and
1.3 Ah back-up battery. The 5 Ah battery and 12 W panel support the systems with telemetry and extended back-up time.
Telemetry
- TCP/IP: The MAWS100 can be connected directly to a LAN
network using the DXE421 ComServer module.
The module converts a standard RS-232 port to a
10/100Base-T Ethernet connection making MAWS
systems Internet-enabled devices. The DXE421 is a compact module installed on the DIN -rail inside the enclosure.
- PSTN: Connection to Public Switched Telephone
Network(s) (PSTN) is made via an industrially hardened
DXM421 modem, which has been designed for demanding
environments and is rated for - 40 to +60 �C operating temperatures. The modem has a low power consumption and includes both data compression and data correction functions.
The maximum data rate is up to 57.6 kbits/second with an excellent in-built line protection.
- GSM/GPRS: The GSMTC35T-M3 is a dual band
GSM terminal especially designed for demanding
professional use. The data modem is small, has low
power consumption and an extended operational temperature range. The tri-band model is available for cellular networks in the USA. The GPRS (General Packet Radio Service) service offers continuous
and high-speed connectivity to the GSM network.
In addition to the standard GSM operation, this option offers additional functions, which greatly facilitate data collection. Data transmission via GPRS can
be initiated by the MAWS100 using FTP (File Transfer
Protocol). The MAWS100 acts as an FTP client placing a file on
the FTP server’s hard disk at user configurable intervals, when
a user set alarm condition is detected by the MAWS100 and/
or when the daily log file(s) are completed. In practice, GPRS
connectivity means the MAWS100 is online all the time and
data is available immediately when required at a very low operating cost. Together with the Vaisala MetMan™ Network
Software, mesoscale or national environmental monitoring
networks can be easily and economically set up as a complete
turnkey solution.
Flexible sensor and telemetry interfacing, advanced statistical calculations, extensive data logging on a compact flash
memory card and versatile data reporting functions
allow the MAWS100 and WXT510 to be customized to a large variety of applications. ●
169/2005 21
LauriTuomaala
ProductLineManager
Vaisala
Helsinki,Finland
USNationalWeatherService
ChoosesVaisala’sModifiedVersionoftheVaisalaWINDCAP®
UltrasonicWindSensorWS425asPartofItsNationwide
SurfaceObservationSystem
Vaisala Ultrasonic Wind Sensors will
be integrated into the Automated
Surface Observing System (ASOS),
which serves as the primary surface
weather observing network in the
United States.
T
he ASOS is jointly administered and used by the
National Weather Service (NWS), the Federal Aviation Administration (FAA), and
the Department of Defense.
The network is designed to support weather forecasting activities, aviation operations, and the
needs of the meteorological, hydrological, and climatological research communities and private
sector communities.
NWS design goals
According to Program Manager Rick Ahlberg, the main objectives of the new ASOS wind
22 169/2005
sensor modernization were: increased reliability, reduced need
for maintenance (particularly in
winter), ice free operation and
the sensors’ ability to incorporate the WMO Gust Standard.
The wind sensor modernization is a part of an overall ASOS
Product Improvement Program.
Mr. Ahlberg says that the improvements include better observing capability, reporting accuracy, and consistency.
The overall program objective was to acquire a commercial
off-the-shelf (COTS) sensor that
could be modified to meet the
requirements of the NWS and
As mentioned before, the fundamental design of the ASOS
Ice Free Wind (IFW) relies on
the standard Vaisala Ultrasonic
Wind Sensor WS425. However,
a few improvements and ASOS
specific modifications have been
made.
In order to guarantee operation even in the most difficult
conditions, the sensor has an enhanced heating feature. There
are heater foils inside the ceramic
transducers, the transducer arms,
and the birdspike. The power
consumption is divided as fol-
Complete Vaisala Ice Free Wind Sensor for the NWS.
Full Production CLIN 5 Vaisala 425NWS sn A0083 v4.30
Rigorous testing
References
Rick Ahlberg, Program Manager; Michael Sturgeon, Test Manager:
ASOS Product Improvement Implementation Plan (Addendum
III) For Ice Free Wind, May 15,
2003. U.S. DEPARTMENT OF
COMMERCE, National Oceanic
and Atmospheric Administration,
National Weather Service/Office of
Operational Systems
Field Systems Operations Center/Observing Systems Branch
Error (es), knots
NWS Sterling Wind Tunnel
8
7
7
5
6
3
5
1
4
-1
3
-3
2
-5
1
-7
0
-9
-1
-11
-2
-13
-3
-15
-4
-17
-5
-19
-6
-21
-7
0
15
30
45
60
75
Error (ed), degrees
During the course of the project,
the sensor was subjected to extensive electrical, environmental,
field, and functional testing.
Test Manager Michael Sturgeon has been responsible for
the tests on the NWS’ side. Although the sensors’ functional
accuracy requirement for wind
speed is +/-2 knots, or 3% up to
125 knots, Michael has also tested the sensor performance beyond its limits. The sensor has
shown good performance with
wind speeds up to 157 knots.
The following graphs show some
of the test results. ●
A083E13.xls bfk
-23
105 120 135 150 165 180 195 210 225 240 255 270 285 300 315 330 345 360
90
Wind Direction, degrees
Average Tunnel Air Speed = 127.9 knots (65.8 m/s)
UUT - Tunnel Air Speed
Delta Wind Direction
Test Method: ISO 16622 section 8.3.1
Wind tunnel test results at 65.8 m/s. Sensor is rotated full 360 degrees,
30 second average wind speed and direction has been recorded.
Full Production CLIN 5 Vaisala 425NWS
v4.2v
Glenn L. Martin Wind Tunnel University Of MD
A079Y15.xls bcg
12
7
10
5
8
3
6
1
4
-1
2
-3
0
-5
-2
-7
-4
-9
-6
-11
-8
-13
-10
-15
-12
-17
-14
-19
-16
Error (ed), degrees
Meeting the NWS
requirements
lows: three transducers total 24
W, three transducer arms total 76
W, and 1 birdspike 15W. The total heating power is 150W.
To ensure the sensor’s ASOS
compatibility, it has a 10m long
sensor cable, power supply with
heating control circuitry, and
power relays to control the heating current. Additionally, in order to guarantee trouble-free
and safe communications, there
is an optical modem that isolates
the sensor from the rest of the
ASOS infrastructure. An installation kit is included in the delivery to make the sensor mechanically compatible with the ASOS
system.
Error (es), knots
FAA. The wind instrument needed to be ice-free, and contain no
moving parts which would wear
down or be contaminated by
sand, salt or dust.
After a rigorous evaluation,
Handar Inc’s COTS sonic sensor was chosen. The sensor was
modified to meet the NWS specifications. In 1999, Vaisala Oyj
acquired Handar Inc. The sensor is now known as the special
ice-free model of the Vaisala Ultrasonic Wind Sensor WS425,
that is, the so-called D-model.
The sensor incorporates Vaisala’s proprietary equilateral triangle design, which always has one
redundant measurement path
and therefore solves the known
turbulence problem.
The Vaisala Ultrasonic Wind
Sensor WS425 is an array of
three equally spaced transducers which radiate and receive
ultrasonic pulses in a horizontal plane. The sensor measures
transit times in both directions
for each of the three transducer
pairs. The wind speed and direction are then derived from these
six transit time measurements.
The Ice Free Wind Sensor for
the NWS is capable of providing
the WMO standard 3-second
average gust, whereas the existing cup anemometer provided a
5-second average gust. This capability improves responsiveness and reflects the gusts more
accurately.
-21
-18
0
15
30
45
60
75
90
105
120
135
150
Wind Direction, degrees
165
180
195
210
225
240
255
270
285
300
315
330
345
-23
360
Average Tunnel Air Speed = 157.6 knots (81.1 m/s)
UUT - Tunnel Air Speed
Delta Wind Direction
Test Method: ISO 16622 section 8.3.1
Wind tunnel test results at 81.1 m/s. Sensor is rotated full 360 degrees,
30 second average wind speed and direction has been recorded.
169/2005 23
Senja Paasimaa
Application Manager
Vaisala
Helsinki, Finland
Factors Affecting Water
Solubility in Oils
Water can occur in three phases
within an oil system, depending on
the chemistry of the oil in question.
This goes for both mineral and
synthetic oil. In general, oils dissolve
some water. However, each oil has its
specific water-saturation point beyond
which excess water becomes either
emulsified or free. Therefore in various
oil-systems, one may have to deal with
dissolved, emulsified, and/or freewater.
24 169/2005
A
solution is a thermodynamically stable state,
where solvating forces homogeneously mix all the
molecules present in the solution. The type and amount of additives mostly determine the water solubility of new oils, whereas oxidation products have a remarkable effect on the solubility
of aged oils.
Oil composition
Pure base oils have very limited solubility, which is related to
the ratios of paraffin, naphthenic,
and aromatic compounds. The
saturation point at 20 °C varies
from approximately 30 parts per
million (ppm) of paraffin oils to
over 200 ppm of fully aromatic liquids, but it is typically between 40 to 80 ppm. Solubility
may increase significantly with
the use of additives. The typical
value for new lubrication oil is
<500 ppm. Oxidation products
also increase solvating efficiency.
Mineral-based transformer oils
typically have very little additives
and therefore have low solubility
like base oil, whereas lubrication
oils with greater amounts of additives generally have much higher solubility (Figure 1).
The overall absorption forces and water content of the solution in the equilibrium state are
determined by Gibb’s energy of
mixing. On the molecular level,
the absorption forces are binding
forces between the water molecules and the molecules in the oil
matrix. Water molecules are polar by nature, so the interaction
forces increase with the increasing polarity of the matrix molecules, such as additives and oxidation products.
Temperature
The dependence of solubility on
temperature is almost always exponential (Figure 1). Hot oil dis-
9000
1600
8000
1400
7000
1200
6000
1000
5000
ppm
ppm
1800
800
4000
3000
600
2000
400
lubrication oil
200
new
used
1000
base oil
0
0
0
20
40
60
80
100
120
0
0.1
0.2
0.3
0.4
T (°C)
0.5
0.6
0.7
0.8
Figure 1: Average water solubility of mineral base oil and one lube oil
as function of temperature.
Figure 2: Solubility of fresh and used engine lubrication oil.
solves greater amounts of water.
The hotter the oil, the greater the
water absorption from air to oil
in the same humidity conditions.
This should be noted in any system setup, as airborne moisture
contamination is one of the most
common water sources.
ter content, thus not giving any
indication whether water is dissolved or free. However, due to
differences in oil types and difficulty in predicting aging effects,
ppm values are often not sufficient. Therefore, relative values
like water activity (aw) are useful
parameters for setting alarms in
control systems.
Capacitive thin film sensors
give this value without temperature corrections or oil-type calibrations. The active film of the
sensor absorbs water molecules,
which change the dielectric constant (i.e. a measure of the ability of a material to resist the formation of an electric field within
it) of the film. The absorption is
proportional to the equilibrium
relative humidity of oil, thus indicating the margin to saturation.
The Vaisala HUMICAP®
thin film polymer sensor products are beneficial in applications
where the water amount must not
exceed solubility limit, i.e. free
water has to be avoided. The sensor is very sensitive even to negligible amounts of water and other
small polar molecules. Therefore,
the active polymer film and the
sensor structure have to be such
that the additives and oxidation
products in oil do not disturb the
measurement. The latest generation of the Vaisala HUMICAP®
sensor is developed for demanding moisture measurement in liq-
Aging of oil
Lubricating oil circulating in
high-speed systems deteriorates
with time due to oxidation. Oil
characteristics - presence of oxygen, catalysts present, and the
temperature levels to which the
oil is exposed - determine the
rate of the aging process. In lubrication oil systems, air is always
present, and the metal debris
from machine construction and
the moisture present are catalysts
for the aging, that is, oil deterioration process. Aging processes are equilibrium reactions, and
therefore the decay rate of oil is a
function of activity of water rather than absolute water content.
High temperatures and mechanical stresses, e.g. in the bearings,
also accelerate the process.
Free water / emulsion
When water content in oil reaches the saturation point of that oil,
it separates out and free water is
formed, resulting in a two-phase
system. Free water is commonly considered as the number one
contaminant of oil. Water corro-
sion and cavitation type damages
are mainly consequences of the
free water phase.
Under a high mixing ratio or
presence of surfactant additives
(i.e. wetting agents that lower the
surface tension of a liquid, allowing easier spreading, and the interfacial tension between two liquids), water may form an emulsion with oil. An emulsion is a
mixture of two unblendable substances, where one substance is
dispersed in the other. Because
of surfactants, micro-size water droplets are homogeneously
mixed in oil, forming an emulsion. The surfactants are chemicals that have both hydrophilic
(a molecule that can bond with
water) and hydrophobic (a molecule that is repelled by water) natures and thus are soluble to both
phase water and oil. They form
micelles (liquid particles) over
the water droplets that convert
the droplets “soluble” in oil. Surfactants may be added to oils to
form emulsion, or some additives
may act as emulsifiers, although
added for different purposes.
Moisture measurement
Traditionally, water in oil has
been measured by Karl Fisher titration (a method for determining the moisture content of
a sample) and expressed in ppm,
which is the total absolute wa-
0.9
1
aw
uid hydrocarbons. The sensor’s
excellent chemical tolerance provides accurate and reliable measurement over a wide measurement range.
ppm conversion
If the solubility of a specific oil
is known through the whole operating temperature range, the
measured relative moisture value can be converted to absolute
water content (ppmw). However,
we must note that the conversion
is valid only if the water solubility of the oil does not change. In
lubrication systems the solubility changes with time regardless
of the system maintenance (Figure 2). In such cases, conversion
to fresh oil does not give a true
value of the water amount. However, an oil regeneration process
may fully restore the original water solubility level of the oil. ●
169/2005 25
Jan Grönblad
Product Line Manager
Vaisala
Helsinki Finland
Long-Term Stability and Low Maintenance:
Dewpoint Measurement at Its Best
V
aisala DRYCAP® technology was launched in
1997. Since then the new
technology has been adopted in
dewpoint applications, like dry
air and other dry gas monitoring.
The main advantage of DRYCAP® technology is its small
drift. This in turn means low
maintenance as the instruments
do not need recalibrating as frequently as other technologies on
the market.
Measuring dewpoint temperature in low
dewpoint applications requires accurate
and reliable dewpoint measurement. A low
maintenance need is a must for industrial
applications, to keep costs at a reasonable
level. Unfortunately low maintenance
requirements and good accuracy do not
often go together. Vaisala DRYCAP®
technology caters for these requirements and
many more.
A variety of
instruments - a variety
of performances
Many different technologies exist
on the market for dewpoint temperature measurement. Some
technologies can offer very good
accuracy, but are sensitive to
drift and may require even daily maintenance. Other technologies have a wider accuracy specification for more industrial use,
and can keep the specified accuracy longer - or at least claim to.
From the users’ point of view it
is unfortunate that the maintenance interval to keep the specified accuracy varies dramatically, depending on the technology
in question. Vaisala DRYCAP®
polymer sensor technology is on
top of the performance charts in
this category, and can maintain
the specified accuracy for years.
Accuracy and long-term
stability
Long-term stability is an important consideration when talking
about accuracy in industrial applications. This means the accuracy of the instrument not only
at the time of manufacture, but
in actual application for months
and years to come. A reasonable
26
169/2005
drift of some degrees can be accepted in most applications, and
calibration at certain intervals is
normal procedure to maintain
accuracy. However, in too many
cases the drift during the manufacturer’s recommended calibration interval is several times
the specified accuracy, which results in poor performance. With
DRYCAP®, the measurement
technology takes care of the accuracy, so that the drift is kept at
minimum. Measurement accuracy with long-term stability is
the basic requirement for all instruments Vaisala develops and
manufactures.
Polymer sensors in low
dewpoint measurement
Vaisala DRYCAP® dewpoint products cater for a wide range of
different measurement needs.
Dewpoint measurement with polymer technology is a very
reliable method for the widest range of applications. At ambient level dewpoints, polymer sensors like the Vaisala HUMICAP® have been used for decades to calculate the dewpoint directly from the measured Relative Humidity and
temperature.
At low dewpoints, like in dry compressed air measurement, sensitivity and long-term stability are more critical issues. Many instruments lack the required sensitivity with the
necessary stability. Vaisala DRYCAP® technology measures
low dewpoint accurately for years. ●
Some years ago, polymer sensors
were accused of having poor accuracy at low dewpoints. This
was true until a suitable technology was developed and launched
in 1997 to use polymer sensors
in low dewpoint measurements.
This patented method is called
Vaisala DRYCAP® technology.
It offers the required sensitivity
for low dewpoints. Its main advantage is its excellent long-term
stability resulting from its combination of polymer material and
automatic self-diagnostics: Autocalibration. DRYCAP® technology provides measurement results within the specified accuracy, month after month and even
year after year. ●
JanGrönblad
ProductLineManager
Vaisala
Helsinki,Finland
VaisalaDRYCAP®Dewpoint
TransmitterDMT340
Versatile
InstallationOptionsfor
DewpointMeasurement
A wide range of products is available
on the dewpoint measurement
market. For fixed installation, a
product that enables users to install
and use the measurement equipment
with ease is warmly welcomed.
W
ith the new Vaisala DRYCAP® Dewpoint Transmitter
DMT340, the installation and
use of the instrument have been
streamlined, as has the utilization of the measurement results.
The new product incorporates
many new features combined
with powerful DRYCAP® measurement technology.
Requirements for dewpoint
measurement differ greatly depending on application and specific customer needs. However, ease of use and reliable measurements are features welcomed by all. The DMT340 series dewpoint transmitter is the
preferred choice in applications
in wich the instrument needs to
be more than just a dewpoint signaling device. The variety of features helps the user to measure
dewpoint easily and reliably, to
reinstall the transmitter when
necessary, and to use many different sensor heads in different
applications.
User interface shows
trends and speaks many
languages
One new feature is the graphic
display that is able to show a
graph of historical measurement
data from the past few hours
to up to one year. This allows
the user to track possible dewpoint changes in the measured
application.
The graphic display has a
menu-based user interface that
speaks many languages. With just
a few clicks, the user can change
the configuration of the instrument, for example to change the
transmitter output scaling, set
the alarm levels of the relays, or
choose which humidity parameters are displayed.
A selection of probes
and installation
accessories
The DMT340 series has four different probes for different appli-
cation needs. All the probes are
pressure-tight and durable under
typical pressures used. For extremes, some of the probes allow
installation under very high pressures. Probes can be installed directly into pipelines or chambers
of measured gas, or additional
probe accessories can be used.
Installation of the DMT348
probe through a ball valve allows
the user to remove the probe
from the measured application
without the need to depressurize
(e.g. a compressed air pipeline).
The probe is drawn in an upright
position with a moveable thread
part and the ball valve is closed
before the probe is removed.
169/2005 27
Vaisala News
A leak screw option is helpful when the installation is in a
location aside from the main gas
flow. The leak screw generates a
small flow that brings a sample
of the main gas flow to the sensor,
improving the response to dewpoint changes.
Two small size probes are
available for small space installations, DMT342 with flange and
DMT347 with thread installation.
Alternative threads are available
for DMT347 as with all DMT340
series probes with thread connection. If the system has high pressure or occasional very high pressure peaks, the rugged DMT344
probe with high-pressure rating
can be used.
One typical installation in low
dewpoint measurement is a sampling system, where the DMT342
probe with sampling cell fits easily due to its compact size. If the
application has a duct where dry
air is measured, the flange installation fits the probe into the thin
wall of a metal duct. Depending
on the installation, the user can
choose from the small DMT342
probe or the DMT348 probe,
which is available in standard
length and long versions.
Installing the
transmitter housing in
various locations is easy
In addition to the versatile probe
installation, the transmitter housing has various installation options. With the additional installation base, detachment is quicker than in the basic installation
where the housing is installed on
a wall. Detaching only requires
the release of the locking screws
holding the transmitter. Another
quick installation method is the
DIN-rail, which the transmitter
can be snapped into.
In some applications, it may
be more suitable to install the
transmitter housing in the gas
pipeline whose dewpoint is to be
measured (e.g. in a compressed
air pipeline). This installation is
done with an accessory available
for pipelines or poles located in
horizontal or vertical positions.
28 169/2005
1
2
3
4
Measured
5 application
6
7
8
9
The housing itself in the
10
DMT340 series transmitter is
11
9.9.2005
Vaisala News
Sample
Gas flow
9.9.2005 1
2
Vaisala News
FILE:
FILE: D MT340 VNew
3
Sample
Gas flow
4 Gas out
1
Measured
5
application
2
6
3Sampling
Sample
cell
7
Gas flow
4
Gas out
Measured 8
IP65/NEMA4X rated and leak
5 application
9 cell (DMT342).
tight, but in 12
outdoor
installations
6 with a sampling
Measuring
the gas sample
Sampling
10
the rain shield option is recom7
cell
11
mended to ensure reliable operaGas out
8
tion in all weather
conditions.
13
9
12
MeasuringSampling
the gas sample with a sampling cell (DMT
10
cell
Electric connections
11
for quick14
and easy
Thread the gas sample with a sampling cell (DMT342).
Measuring
13
reinstallation
connection
12
Measuring the gas sample with a sampling cell (DMT342).
The DMT340 series also offers
15 for cabling the
many options
14
Thread
13
dewpoint measurement
connection
Measured signal
application
and the low voltage
supply. Connectors are 16
recommended. The
15
14
Thread
standard M12 series connecMeasured connection
tors offer the fastest and easiapplication
17
est cabling reinstallation, within
16
15
Flange
seconds.
Probe
installed directly in
connection
Basic cable
Measured
18 installation is
the measured
application
application 17
done through a normal cable
with 16
flange (e.g. DMT342)
or
gland to a screw terminal inside
with thread (e.g. DMT344 or
Flange
DMT347)
the transmitter.
19 In harsh
Probeenvironinstalled directly
in the measured application with flangeconnection
(e.g. DMT342) or with thread (e.g
18
ments where20cablesDMT347)
are installed
17
inside a conduit, an optional
Flange
conduit fitting can be used. If
connection
c) application w
19
Probe
installed directly in the measured
21
the cables are hidden behind a
18
20
DMT347)
wall, the transmitter can be flush
b)
mount on the standard electrical
a)
22 and the cable led
19
Probe installed directly in the measured application with flange (e.g.
mounting box,
21
20
DMT347)
through the hole in the back of
Ball valve
Ball valve
the transmitter.
23
open
closed
a)
A ready installed mains cable
22
21
option with different plug
b)
options is also
Ball valve
24 available to
make the installation as
23
open
a)
22
easy as plug and play.
Measured pressurized pipeline
25
Pioneering
technology
23
24
Ball valve
open
DMT348 installation with the ball valve set.Measured
Probe in
normal
pressurized pipeline
The DMT340
de- installation
26has been
HMP368
with the ball
valve (a),
set. probe
Probelifted
in normal
position
measurement
position
up to measurement
close the ball valve
(b),(a), probe lifted
25
27 and versatile
the ball valve
after24
which the
the probe
probe
canbe
beremoved
removedfrom
fromthe
thepressurized
pressurizedpipeline
pipeline
(c).
signed for easy
instal-(b), after
which
can
(c).
lation. Reinstallation can be done
.200doesn’t
5
FILE: D
MT340 pipeline
VNews
Measured
pressurized
quickly and28
easily.9.9This
26
HMP368 installation with the ball valve set. Probe in
Vaisala News
25
mean that DMT340 needs more
27
the ball valve (b), after which the probe can be remove
maintenance than other transmitSample
28
Leak
ters, quite the contrary. The VaisaGas
flow
28
screw
26
HMP368 installation with the
ball valve set. Probe in normal measure
la DRYCAP® dewpoint measure27
the ball valve (b), after which the probe can be removed from the pres
ment technology
29 incorporated in
the DMT340 series offers good
28
long-term stability, that is, small
drift combined
30 with fast response
time and durability. This superior
and patented technology is the re31 pioneering work
sult of Vaisala’s
Gas flow
for more than 30 years in humidity measurement with thin film
32 technology.
Installation
in a pressurized
with the help
of leak
(DMT348).
Installation
in T-piecepipeline
in a pressurized
pipeline
withscrew
the help
of leak The response
polymer sensor
● in T-piece
33
reasonable with thescrew
help (DMT348).
of small flowThe
generated
the part
pipeline with
otherwise
responseintime
is stillofreasonable
with
the help zero
of flow.
small flow generated in the part of pipeline with otherwise zero flow.
Briefly Noted
Vaisala BAROCAP® Celebrates its 20th Anniversary
S
ilicon micromechanical sensors were first developed by
Vaisala in the early 1980s. The
development of a silicon absolute pressure sensor was a direct
continuation of Vaisala’s work on
a similar type of aneroid pressure
sensor. The Vaisala BAROCAP®
was first introduced commercially in 1985.
The Vaisala BAROCAP®
pressure sensor combines two
powerful techniques: single
crystal silicon as a spring material, and the capacitance detection principle. These techniques
give the BAROCAP® its superior performance in terms of wide
dynamic range, low hysteresis,
excellent repeatability and long-
term stability - the last of which
is widely recognized as the single
most important characteristic of
a barometric pressure sensor.
After 20 years of continuous
development and field experience, the Vaisala BAROCAP®
offers outstanding performance
wherever used. Perhaps the longest journey from the manufacturing line was made by those BAROCAP® sensors that in January 2005 successfully landed on
the surface of Titan, a moon of
the planet Saturn, measuring the
pressure in its atmosphere as part
of the Huygens probe.
Today Vaisala offers a full
range of barometers used by several meteorological institutes and
aviation organizations around
the world, as well as in demanding laboratory and industrial ap-
plications. ●
World Championships in Athletics - Helsinki
T
he Finnish Meteorological Institute, Vaisala, and partners
launched the first measurement
campaign in the Helsinki Testbed project in August 2005. Helsinki Testbed is a dense weather
measurement network suitable
for forecasting mesoscale weather phenomena - within a relatively small area and short period of time. The first measurement campaign benefited the organizers, competitors, audience
and meteorologists of the 2005
World Championships in Athletics, held in Helsinki in August.
In cooperation with the Finnish
Athletics federation and the City
of Helsinki, several additional
weather observation sites were
installed at several locations,
such as along the marathon route
and at the Olympic Stadium. ●
Markus Juvonen installing the Vaisala Weather Transmitter WXT510
at the Stadium Tower as one of the Helsinki Testbed weather
observation sites. The WXT510 measures wind speed and direction,
liquid precipitation, barometric pressure, temperature and relative
humidity - all in one transmitter.
169/2005 29
Briefly Noted
Vaisala Website Receives a Face Lift
T
he Vaisala website has undergone major structural and
visual changes. Vaisala’s businesses - Instruments, Soundings, Thunderstorm, Windprofilers, Road and Rail Weather,
HydroMet and Aviation Weather - all have their own sub-sites
within the new site. The corporate section serves as an umbrel-
la with information on the Vaisala Group, news, and services for
future Vaisala employees, as well
as investors. Check out the new
site at: www.vaisala.com. ●
Introducing Vaisala Returns On The Web
R
eturns On The Web is a selfservice webshop where you
can create your own service order. The system produces the required paperwork, including a
ready-made, prepaid waybill for
shipping. It also provides contact information for arranging
the pickup.
Shipping to service
Returns On The Web makes
shipping to the Vaisala Service
Center fast and easy. The system
has in-built logistics which route
the returned units to the defined
service center.
Returns On The Web has integrated the creation of shipping
documents. It communicates
electronically with couriers, automatically creating the waybill
labels for shipping. The waybills
are printed with a normal laser
printer and then placed in a document pouch on top of the package for shipping.
A service order placed in Returns On The Web replaces the
need to obtain a separate RMA
from Vaisala.
How to begin using the
system
Simply go to http://www.vaisala.
com/returns
You can log in to the system
as a new user; after you use the
system for the first time the system issues you a user ID and
password. The next time you
log in, the system remembers
most of your information - and
processing a service request is
even faster!
Service availability
The service is being gradually
implemented to serve customers
in different countries. The service home page shows the countries in which the system can
be used. ●
http://www.vaisala.com/returns
- Returns Made Easy
1. Log in to the system anonymously or with your login
2. Select the product that needs service and the desired service
3. Type in customer information and billing details
4. System generates shipping documents, call courier for
pickup
An animated picture tells more than thousand words - see the
service introduction video at http://www.vaisala.com/returns
30 169/2005
Briefly Noted
NewCalibrationFacilitiesatVaisalaFactory
V
aisala Instruments has invested in improved ambient
conditions for calibration at its
Finnish factory. The new facilities consist of two separate laboratories, each covering a 150m2
space. Both were taken into use
in February 2005.
The new facilities ensure stable and uniform temperature
and relative humidity conditions throughout the year. Error
and variation in calibration are
avoided by keeping the measurement equipment and the products being calibrated under stable conditions.
In the Finnish climate where
summers are warm and humid
and winters cold and dry, conditions are kept stable by heating, cooling, dehumidifying and
humidifying the inlet air. Excess heat generated by equip-
ment and operators is steered
out. Conditions are monitored
using Vaisala HUMICAP® Humidity and Temperature Transmitters HMT330.
The new facility is fully EMC
protected. Special windows, metal plates under the elevated floor,
and conductive tape connecting
the pieces together creates full
protection from EMC disturbance from outside. The increasing use of cell phones instead of
office phones is the main reason
for this demand.
You can enjoy the benefits of
our investment in the quality and
reliability of Vaisala instruments.
The factory and service calibrations provided by Vaisala continue to meet the ever-tightening
quality requirements. ●
VaisalaExpandstotheNetherlands
V
aisala has employed two new
members of staff in order to
strengthen its market position
in the Netherlands. With the arrival of Robert-Jan Pouw (Area
Sales Manager) and Sebastian
Schimmack (Customer Service
Engineer), Vaisala’s customers
in the Netherlands can be served
directly.
In addition, Vaisala has established a new Customer Service Center for Europe. Through
the establishment of the new
service center in Bonn and the
employment of multilingual
Dutch speaking workers, Vaisala
is realizing part of a range of initiatives to serve customers directly. Now it is also easier for customers to contact Vaisala by dialing the worldwide toll free telephone number, which is simply
00800-2VAISALA.
Vaisala has been producing
measurement instruments since
Sebastian Schimmack and Robert-Jan Pouw.
1936, and an authorized distributor, CaTeC, has been marketing
Vaisala’s instruments in the Netherlands for two decades. CaTeC
will continue to do so in co-operation with Vaisala. ●
Vaisala Customer Service Center
for Europe:
Vaisala GmbH
Adenauerallee 15
D - 53111 Bonn
Germany
International Toll Free Number:
00800 2VAISALA
(00800-28247252)
ContacttheVaisalaNewsTeam
For subscriptions, cancellations, feedback and changes of
address, please contact the Vaisala News team by sending
an email to
[email protected]
Thank you for your interest.
Marikka Metso
Editor-in-Chief
169/2005 31
Vaisala Oyj
P.O. Box 26, FI-00421 Helsinki
FINLAND
Telephone: +358 9 894 91
Telefax: +358 9 8949 2227
Vaisala Oyj
Malmö Office
Drottninggatan 1 D
S - 212 11 Malmö
SWEDEN
Telephone: +46 40 298 991,
in Sweden: 0200 848 848
Telefax.: +46 40 298 992,
in Sweden: 0200 849 849
Vaisala GmbH
Hamburg Office
Schnackenburgallee 41
D-22525 Hamburg
GERMANY
Telephone: +49 40 839 030
Telefax: +49 40 839 03 110
Vaisala GmbH
Bonn Office
Adenauerallee 15
D-53111 Bonn
GERMANY
Telephone: +49 228 24 9710
Telefax: +49 228 249 7111
Vaisala GmbH
Stuttgart Office
Pestalozzi Str. 8
D-70563 Stuttgart
GERMANY
Telephone: +49 711 734 057
Telefax: +49 711 735 6340
Vaisala Ltd
Birmingham Operations
Vaisala House
349 Bristol Road
Birmingham B5 7SW
UNITED KINGDOM
Telephone: +44 121 683 1200
Telefax: +44 121 683 1299
Vaisala Ltd
Newmarket Office
Unit 9, Swan Lane
Exning
Newmarket
Suffolk CB8 7FN
UNITED KINGDOM
Telephone: +44 1638 576 200
Telefax: +44 1638 576 240
Vaisala SAS
Paris Office
2, rue Stéphenson (escalier 2bis)
F-78181 Saint-Quentin-en-Yvelines
Cedex
FRANCE
Telephone: +33 1 3057 2728
Telefax: +33 1 3096 0858
North America
Vaisala Inc.
Boston Office
10-D Gill Street
Woburn, MA 01801
USA
Telephone: +1 781 933 4500
Telefax: +1 781 933 8029
Vaisala Inc.
Columbus Office
1372 Oxley Road
Columbus, Ohio 43212
USA
Vaisala Inc.
Boulder Operations
194 South Taylor Avenue
Louisville, CO 80027
USA
Telephone: +1 303 499 1701
Fax: +1 303 499 1767
Vaisala Inc.
San Jose Office
6980 Santa Teresa Blvd
Suite 203
San Jose, CA 95119-1393
USA
Telephone: +1 408 578 3670
Telefax: +1 408 578 3672
Vaisala Inc.
Tucson Operations
2705 East Medina Road
Tucson, Arizona 85706, USA
Telephone: +1 520 806 7300
Telefax: +1 520 741 2848
U.S. Toll Free 1 800 283 4557
Vaisala Inc.
Houston Office
1120 Nasa Road 1 Suite 220-E
Houston, TX 77058
Telephone: +1 281 335 9955
Telefax: +1 281-335-9956
Vaisala Inc. Regional Office Canada
37 De Tarascon
Blainville
QC J7B 6B7
CANADA
Telephone: +1 450 430 0880
Telefax: +1 450 430 6410
Asia and Pacific
Vaisala KK
Tokyo Office
42 Kagurazaka 6-Chome
Shinjuku-Ku
Tokyo 162-0825
JAPAN
Telephone: +81 3 3266 9611
Telefax: +81 3 3266 9610
Vaisala Pty Ltd
Melbourne Office
3 Guest Street
Hawthorn, VIC 3122
AUSTRALIA
Telephone: +61 3 9818 4200
Telefax: +61 3 9818 4522
Vaisala China Ltd.
Floor 2, EAS Building
No. 21, Xiao Yun Road
Dongsanhuan Beilu
Chaoyang District
Beijing 100027
People’s Republic of China
Telephone: +86 10 8526 1199
Telefax: +86 10 8526 1155
Vaisala Beijing Representative Office
in Shanghai
c/o Kaukomarkkinat
Room 402A West Tower, Sun Plaza
88 Xian Xia Road
Shanghai, P.R. China 200336
Telephone: +86 21 62700642/41
Telefax:+86 21 62700640
Vaisala Regional Office Malaysia
Level 36, Menara Citibank
165 Jalan Ampang
50450 Kuala Lumpur
MALAYSIA
Telephone: +60 3 2169 7776
Telefax: +60 3 2169 7775
C210036EN 2005-10
Europe
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