P.O. Box 26, FI-00421 Helsinki, Finland
Tel. +358 9 894 91
Fax: +358 9 8949 2485
Email: [email protected]
DMT345 and DMT346 Dewpoint Transmitters
for High Temperature Applications
• The DMT345 measures humidity in
temperatures up to 180°C (356 °F)
• The DMT346 measures humidity in
temperatures up to 350 °C (+662 °F)
• Dewpoint accuracy ±2 °C (±3.6 °F)
• Vaisala DRYCAP® Sensor provides
accurate, reliable measurement
with excellent long-term stability
and fast response
• Withstands condensation
• Unique auto-calibration feature
• Optional local display with keypad,
mains power supply module and
alarm relays
• NIST traceable calibration
(certificate included)
The Vaisala DRYCAP® Dewpoint Transmitters DMT345 and DMT346 are designed to
measure and control humidity especially in dry environments with high temperatures.
The Vaisala DRYCAP® Dewpoint
Transmitters DMT345 and DMT346 are
designed for humidity measurement
in industrial drying applications with
particularly high temperatures.
Both transmitters incorporate the
Vaisala DRYCAP® sensor, which is
accurate, reliable, and stable. The
sensor withstands condensation and is
immune to particulate contamination,
oil vapor and most chemicals. The
DRYCAP® sensor stands out for its swift
response time and rapid recovery after
getting wet.
Measure humidity directly
in hot processes
The DMT345 and DMT346 are
constructed for direct measurement
in hot processes. Therefore, there is no
need for sampling systems and trace
heating. As a result, high accuracy and
constancy are maintained.
The accuracy and stability of the
DMT345 and the DMT346 are due to
the unique auto-calibration function,
patented by Vaisala. This auto-
calibration makes the transmitter
perform a calibration and adjustment
by itself while the measured process is
running. If the measurement accuracy
is not confirmed, corrections are made
automatically. The procedure is so
quick and corrections are so minor that
it will go unnoticed. This ensures low
maintenance and high performance. In
normal conditions, it is recommended
to have a traceable calibration
performed once a year.
DMT345, Accurate in hot
and dry environments
The DMT345 is designed for accurate
humidity measurement in hot and
dry conditions. This model provides
unmatched dry end measurement
accuracy in temperatures up to
140 °C, however the DMT345 can
operate safely in temperatures up to
180 °C.
The stainless steel probe is especially
designed for high temperatures and
has an optional installation flange that
allows an adjustable installation depth
and therefore a precise positioning.
DMT346, Reliable in very
hot processes
When process temperatures range
between 140 °C to 350 °C,
the DMT346 provides the best
measurement performance.
The DMT346 comes with a cooling set
as a standard feature. The cooling effect
may be regulated by adding the cooling
fins, or removing them from the set for
the best measurement performance.
The cooling system operates without
moving parts, additional power or
cooling utilities, thereby eliminating
The large and clear display allows the user
to check data at a glance.
DMT345 and DMT346
the risk of sensor damage due to a
mechanical cooling failure.
Additionally, sensor warming
minimizes the risk of condensing
on the sensor. In low humidity the
combination of auto-calibration
and DRYCAP® ensures accurate
the user to clearly monitor operational
data, measurement trends and up to
one-year measurement history.
Versatile options
A wide variety of power supply options
are also available. For serial interface
the USB connection, RS232 and
RS485 can be used. Additionally an
alarm relay option is offered. Units are
delivered installation-ready and meet
ROHS requirements.
The display/keypad option simplifies
operation. Output variables and other
settings can be changed with the
multilingual menu-based commands.
The DMT345 and DMT346 transmitters
can be ordered with a large numerical
and graphical display, which allows
Technical Data
Measured variables DMT345
Dewpoint DMT345
Measurement range
Measured variables DMT346
Vaisala DRYCAP®180S
-40 ... +100 °C (-40 ...+212 °F) Td
±2°C (±3.6 °F) Td
See the accuracy graph below
Response time 63% [90%] flow rate 1 l/min and 1 bar pressure
from dry to wet
5s [10 s]
from wet to dry including auto-calibration
45s [5 min]
Temperature DMT345
Measurement range
with sensor warming
Temperature sensor
Dewpoint DMT346
Measurement range
Vaisala DRYCAP®180S
-25 ... +100 °C (-13 ...+212 °F) Td
±2°C (±3.6 °F) Td
See the accuracy graph below
Response time 63% [90%] flow rate 1 l/min and 1 bar pressure
from dry to wet
5s [10 s]
from wet to dry including auto-calibration
45s [5 min]
Mixing Ratio DMT346
0...+180 °C (+32...+356°F) Measurement range (typical)
0...1000 g/kg (0..7000 gr/lbs)
upper range limited by humidity (at Accuracy (typical)
±12% of reading
80% RH warming is switched on and T
reading not actual process Temperature)
±0.4 °C at 100 °C
Pt 100 IEC 751 1/3 class B Vaisala products for humidity measurement in hot processes
Relative Humidity DMT345
Measurement range
with sensor warming
below 10% RH
above 10% RH
±10% of reading
±1,5% RH + 1,5% of reading
Mixing Ratio DMT345
Measurement range (typical)
Accuracy (typical)
0...1000 g/kg (0..7000 gr/lbs)
±12% of reading
0...100% RH
0...80% RH
Technical Data for DMT345 and DMT346
Dimensions in mm (inches)
DMT345 probe and mounting flange
Pressure range for probes
slight pressure difference (~ 200 mbar)
Measured gases
non corrosive gases
Complies with EMC standard EN61326-1, Electrical equipment for
measurement, control and laboratory use EMC requirements; Industrial environment.
Up to +180 °C (+356 °F) for DMT345
Up to +350 °C (+662 °F) for DMT346
-40...+60 °C (-40...+140 °F)
0...+60 °C (32…+140 °F)
-55...+80 °C (-67…+176 °F)
Inputs and outputs, both models
Mechanics, both models
Cable bushing
Conduit fitting (optional)
User cable connector (optional)
option 1
option 2
USB-RJ45 Serial Connection Cable
Probe cable diameter
Probe cable lenght
Housing material
Housing classification
Housing weight
(2 standard, 3rd optional)
0...20 mA, 4...20 mA
0...1 V, 0...5 V, 0...10 V
± 0.05 % full scal
40.6 (1.6)
120 (4.72)
ø89 (3.5)
ø20 (0.79)
max 25 mA
max 60 mA
max 25 mA
+ 20 mA
+ 110 mA max
112.5 (4.43)
8 15 (0.59)
(fixed on top of
the cooling set)
cooling element
125 (4.92)
DMT346 Probe
stainless steel
steel grid
± 0.005 %/°C full scale
cooling fins
2, 52,5
or 10
or m
10 m
357 (14.1)
334.5 (13.17)
RL< 500 ohm
RL > 2 kohm
RL > 10 kohm
0.5 mm2 (AWG 20) stranded
wires recommended
RS-232, RS-485 (optional)
RS-232, USB
0.5 A, 250 VAC, SPDT
LCD with backlight, graphic
trend display
English, French, Spanish,
Chinese, German, Japanese,
Russian, Swedish, Finnish
M20x1.5 For cable diameter
M12 series 8- pin (male)
with plug ( female) with 5 m /
16.4 ft black cable
with plug ( female) with
screw terminals
part. no 219685
5.5 mm
2 m, 5 m or 10 m
G-AlSi 10 Mg (DIN 1725)
IP 65 (NEMA 4X)
1.2 kg
ø 11
ø13.5 (0.53)
22.5 (0.89)
DMT345 and DMT346 Transmitter housing
183 (7.20)
169 (6.65)
DRYCAP® is a registered trademark of Vaisala.
Specifications are subject to change without prior notice.
© Vaisala Oyj
Ref. B210692EN rev. A 2007 - 8
Display menu languages
about 6 min
ø7 (0.28)
Digital outputs
Service connection
Relay outputs 2+2 pcs (optional)
Display (optional)
304 (11.97)
164 (6.46)
77 (3.03)
External loads
current outputs
0...1V output
0...5V and 0...10V outputs
Max wire size
DMT346 Cooling set
96 (3.78)
Accuracy of analog outputs at 20 °C
Temperature dependence of the
analog outputs
10...35 VDC, 24 VAC
100...240 VAC 50/60 Hz
71 (2.80)
Analog outputs
current output
voltage output
116 (4.57)
Operating voltage
with optional power supply module
Default start-up time
initial reading after power-up
full operation after sensor Purge
and Autocal
Power consumption @ 20 °C (Uin 24
Uout 2x0...1V/0...5V/0...10V
Iout 2x0...20mA
display and backlight
during sensor purge
ø105 (4.13)
ø118 (4.65)
ø28 (1.1)
Mechanical durability
of probe heads
for transmitter body
with display
Storage temperature range
Operating Environment, both models
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