Vaisala | DRYCAP DMT345 | DMT345 and DMT346 Dewpoint Transmitters for High
DMT345 and DMT346 Dewpoint Transmitters
for High Temperature Applications
The large graphical display allows the
user to check data at a glance.
Vaisala DRYCAP® Dewpoint Transmitters DMT345 and DMT346 are designed
to measure and control humidity, especially in dry environments with high
The Vaisala DRYCAP® Dewpoint
Transmitters DMT345 and
DMT346 are designed for humidity
measurement in industrial drying
applications with particularly high
Both transmitters incorporate the
Vaisala DRYCAP® sensor, which is
accurate, reliable, and stable. The
sensor is condensation-resistant
and is immune to particulate
contamination, oil vapor, and most
chemicals. The DRYCAP® sensor is
notable for its swift response time
and rapid recovery after getting wet.
Measure Humidity Directly
in Hot Processes
The DMT345 and DMT346 are
built for direct measurement in
hot processes. Therefore, there
is no need for sampling systems
and trace heating. As a result,
high measurement accuracy and
constancy are maintained.
The accuracy and stability of the
DMT345 and the DMT346 are due to
their unique auto-calibration function,
developed by Vaisala. This feature
allows the transmitter to perform
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 so
minor that it causes no disruption,
ensuring easy 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 at temperatures up to 140 °C;
however, it can operate safely at
temperatures up to 180 °C.
The DMT345 measures
humidity at temperatures up to
180 °C (356 °F)
The DMT346 measures
humidity at temperatures up to
350 °C (+662 °F)
Dew point accuracy ±2 °C
(±3.6 °F)
Vaisala DRYCAP® sensor
provides accurate and reliable
measurement with excellent
long-term stability and fast
response time
Graphical display and keypad
for convenient operation
Optional alarm relays and
mains power supply module
Analog outputs, RS232/485,
MODBUS protocol support
Unique auto-calibration feature
NIST traceable calibration
(certificate included)
The stainless steel probe is especially designed for high
temperatures and has an optional installation flange for
easy adjustment of the probe’s installation depth and,
therefore, more precise positioning.
DMT346: Reliable in Very Hot Processes
The DMT346 provides the best measurement performance
at process temperatures between 140 °C and 350 °C.
The DMT346 includes a cooling set as standard. The
cooling effect can be regulated by adding the cooling
fins, or they can be removed from the set for optimal
measurement performance.
The cooling system has no moving parts, and requires no
additional power or cooling utilities, so there is no risk of
sensor damage due to mechanical cooling failure.
Additionally, sensor warming minimizes the risk of
condensation accumulating on the sensor. In low humidity
conditions the combination of auto-calibration and
DRYCAP® ensures accurate measurement.
Graphical Display of Measurement Data
and Trends for Convenient Operation
The DMT345 and DMT346 transmitters feature a large
numerical and graphical display with a multilingual menu
and keypad. It allows users to easily monitor operational
data, measurement trends, and access measurement
history for the past 12 months.
The optional data logger, with real-time clock, makes
it possible to generate over four years of measurement
history and zoom in on any desired time or time frame.
The display alarm allows tracking of any measured
parameter, with freely configurable low and high limits.
Versatile Outputs and Data Collection
DMT345 and DMT346 transmitters can support up to three
analog outputs; an isolated galvanic power supply and
relay outputs are also available.
For serial interface the USB connection, RS232, and RS485
can be used.
DMT345 and DMT346 are also capable of applying
the MODBUS communication protocol and, together
with an appropriate connection option, provide either
MODBUS RTU (RS485) or MODBUS TCP/IP (Ethernet)
The data logger, with real-time clock and battery backup,
guarantees reliable logging of measurement data for over
four years. The recorded data can be viewed on the local
display or transferred to a PC with Microsoft Windows®
software. The transmitter can also be connected to a
network with an optional (W)LAN interface, which enables
a (wireless) Ethernet connection. A USB service cable
makes it easy to connect the DMT345/346 to a PC via the
service port.
Units are delivered installation-ready.
Technical Data
Measured Variables DMT345
teMperature DMt345
Dew point DMt345
Dew point temperature (°C)
Measurement range
Vaisala DRYCAP®180S
-40 ... +100 °C (-40 ... +212 °F) Td
±2°C (±3.6 °F) Td
See the accuracy graph below
at u
t io
± 4°C Td
or better
Accuracy ±2°C Td
or better
ac t i v
f ie d ,
wer li
not s
ge lo
A cc u
re m e
e a su
int m
D ew
Dew point accuracy
vs. measurement
conditionsgas (°C)
of measured
Dew point accuracy vs. measurement conditions
Response time 63% [90%] flow rate 1 l/min and 1 bar pressure
from dry to wet
5 s [10 s]
from wet to dry including auto-calibration
45 s [5 min]
Measurement range
with sensor warming
Temperature sensor
0 ... +180 °C (+32 ... +356°F)
upper range limited by humidity
(at 80 %RH warming is switched on and T
reading not actual process temperature)
±0.4 °C at 100 °C
Pt100 RTD Class F0.1 IEC 60751
relative HuMiDity DMt345
Measurement range
with sensor warming
below 10 %RH
above 10 %RH
0 ... 100 %RH
0 ... 80 %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
Technical Data
Measured Variables DMT346
Dew point DMt346
Measurement range
Vaisala DRYCAP®180S
-25 ... +100 °C (-13 ... +212 °F) Td
±2 °C (±3.6 °F) Td
See the accuracy graph below
Temperature dependence of
analog outputs
External loads
current outputs
0 ... 1V output
0 ... 5V and 0 ... 10V outputs
Max. wire size
± 0.005%/°C full scale
Inputs and Outputs, DMT345 and DMT346
Mechanics, DMT345 and DMT346
Operating voltage
10 ... 35 VDC, 24 VAC ±20%
with optional power supply module
100 ... 240 VAC 50/60 Hz
Default start-up time
initial reading after power-up
full operation after sensor purge and autocalibration about 6 min
Power consumption @ 20 °C (Uin 24 VDC)
max. 25 mA
Uout 2x0 ... 1V/0 ... 5V/0 ... 10V
max. 60 mA
Iout 2x0 ... 20mA
max. 25 mA
display and backlight
+ 20 mA
during sensor purge
max. + 110 mA
Analog outputs
(2 standard, 3rd optional)
current output
0 ... 20 mA, 4 ... 20 mA
voltage output
0 ... 1 V, 0 ... 5 V, 0 ... 10 V
Accuracy of analog outputs at 20 °C
± 0.05% full scale
Cable bushing
Dew point temperature (°C)
Mechanical durability
up to +180 °C (+356 °F) for DMT345
of probes
up to +350 °C (+662 °F) for DMT346
of transmitter body
-40 ... +60 °C (-40 ... +140 °F)
with display
0 ... +60 °C (32 … +140 °F)
Storage temperature range
-55 ... +80 °C (-67 … +176 °F)
Pressure range for probes slight pressure difference (~ 200 mbar)
Measured gases
non-corrosive gases
Electromagnetic compatibility
Complies with EMC standard
EN61326-1, Industrial environment
Note: Transmitter with display test impedance of
40 ohm is used in IEC61000-4-5 (Surge immunity)
RL< 500 ohm
RL > 2 kohm
RL > 10 kohm
0.5 mm2 (AWG 20) stranded
wires recommended
Digital outputs
RS232, RS485 (optional)
Service connection
RS232, USB
Relay outputs 2+2 pcs (optional)
0.5 A, 250 VAC, SPDT
Ethernet interface (optional)
Supported standards
8P8C (RJ45)
IPv4 address assignment
DHCP (automatic), static
WLAN interface (optional)
DHCP (automatic), static
Supported standards
Antenna connector type
IPv4 address assignment
DHCP (automatic), static
WEP 64/128, WPA WPA2/802.11i
Authentication / Encryption (WLAN)
Open / no encryption
Open / WEP
WPA Pre-shared key / TKIP
WPA Pre-shared key / CCMP (a.k.a. WPA2)
Optional data logger with real-time clock
Logged parameters
max. four with trend/min/max values
Logging interval
10 sec. (fixed)
Max. logging period
4 years, 5 months
Logged points
13.7 million points per parameter
Battery lifetime
min. 5 years
LCD with backlight, graphical trend display
Menu languages
English, Chinese, Finnish, French, German,
Japanese, Russian, Spanish, Swedish
Dew point accuracy vs. measurement conditions
Response time 63% [90%] flow rate 1 l/min and 1 bar pressure
from dry to wet
5 s [10 s]
from wet to dry including auto-calibration
45 s [5 min]
Mixing ratio DMt346
Measurement range (typical)
Accuracy (typical)
0 ... 1000 g/kg (0 ... 7000 gr/lbs)
±12% of reading
Operating Environment, DMT345 and DMT346
M20x1.5 for cable diameter
8 ... 11mm/0.31 ... 0.43"
Conduit fitting (optional)
User cable connector (optional)
M12 series 8-pin (male)
option 1
female plug with 5 m (16.4 ft.) black cable
option 2
female plug with screw terminals
USB-RJ45 Serial Connection Cable
Probe cable diameter
5.5 mm
Standard probe cable lengths
2 m, 5 m or 10 m
(Additional cable lengths available, please
see order forms for details)
Housing material
G-AlSi 10 Mg (DIN 1725)
Housing classification
IP 66
IP65 (NEMA4X) with local display
depending on selected probe, cable, and modules
1.0 – 3.0 kgs
Technical Data
Dimensions in mm (inches)
DMT345 probe and mounting flange
DMT345 and DMT346 transmitter housing
75 (2.96)
28 (1.10)
75 (2.95)
12 (0.47)
77 (3.03)
71 (2.80)
13.5 (0.53)
50 (1.97)
41 (1.61)
27 (1.06)
2 (0.08)
drilling 16...22 (0.63...0.87)
192 (7.56)
242 (9.53)
183 (7.20)
169 (6.65)
DMT346 cooling set
304 (11.97)
164 (6.46)
112.5 (4.43)
40.6 (1.6)
120 (4.72)
ø105 (4.13)
ø118 (4.65)
ø28 (1.1)
8 15 (0.59)
ø89 (3.5)
ø20 (0.79)
ø7 (0.28)
96 (3.78)
116 (4.57)
(fixed on top of
the cooling set)
cooling element
125 (4.92)
cooling fins
DMT346 probe
Stainless steel grid
cable 2 m, 5 m or 10 m
357 (14.1)
334.5 (13.17)
ø 11
ø13.5 (0.53)
22.5 (0.89)
DRYCAP® is a registered trademark of Vaisala.
please contact us at
ref. B210723en-F ©vaisala 2013
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prohibited. all specifications — technical included — are subject
to change without notice.
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