Vaisala DMT340 Series Dew Point & Temperature Meter


  • Measures dew point from -70 … +80 °C (-94 … +176 °F) with an accuracy of ±2 °C (±3.6 °F)
  • Condensation-resistant
  • Unique auto-calibration feature maintains accuracy over long term
  • Compatible with Vaisala DRYCAP Handheld Dew Point Meter DM70
  • Traceable calibration to measurements and analog outputs (certificates included)
  • Graphical display and keypad for convenient operation
  • Optional alarm relays and mains power supply module
  • Up to three analog outputs, RS-232/485, LAN
  • Modbus protocol support (RTU/TCP)

Dpstar is a leading supplier of environmental measurement sensors for temperature, relative humidity, pressure, dew point, CO2, and other environmental condition monitoring for industrial process application and research. Since the ’90s, we earned a reputation as a trusted partner to our clients through our commitment and dedication. We are an authorized distributor and supplier of measuring sensors solutions from renowned manufacturers Vaisala. Vaisala is a global leader in environmental and industrial measurement. Building on 80 years of experience, Vaisala provides observations for a better world. Vaisala is a reliable partner for customers around the world, offering a comprehensive range of innovative observation and measurement products and services.

Condensation-resistant DMT340 is designed for industrial low-humidity applications such as industrial drying, compressed air systems, semiconductor industry, dry rooms, baking ovens, and metal heat treatment to provide accurate and reliable measurement.

There are several models for different types of needs:

DMT341 for wall-mounting

DMT341 display shows measurement trends, real-time data, and measurement history. DMT341 is made for installations in dry rooms where the entire dew point transmitter needs to be inside the dry space. The concept is easy to clean and suitable also for cleanrooms.

DMT342 with small size flanged probe for use with sampling cell

The DMT342 probe is installed using a flange or sampling cell. The small probe is ideal for integration into larger equipment or applications with high pressures.

DMT344 for pressurized processes

The DMT344 features a threaded connection for extended pressures with different fitting-body options. It is ideal for permanent installation into pressurized or vacuum processes.

DMT347 with small pressure-tight probe

The DMT347 probe is ideal for pressurized or vacuum applications in tight spaces. The small probe is installed using Swagelokâ connectors.

DMT348 for pressurized pipelines

The DMT348 is ideal for installation into pressurized or vacuum processes where the probe needs to be able to be removed while the process is running. The probe depth is adjustable.

Key Benefits

Choose the probe suitable for your needs
Five different probe types designed to meet various requirements.

Easy maintenance
The Vaisala DRYCAP sensor is immune to particulate contamination, water condensation, oil vapor, and most chemicals.

Stable measurement
The auto-calibration feature allows the transmitter to perform calibration and adjustment by itself while the measured process is running.


Model DMT342 DMT344 DMT347 DMT348
Pressure range 0 … 50 bar/0 … 725 psia 0 … 50 bar/0 … 725 psia 0 … 10 bar/0 … 145 psia 0 … 40 bar/0 … 580 psia
Mechanical durability Up to 250 bar/3625 psia Up to 100 bar/1450 psia Up to 10 bar/145 psia Up to 70 bar/1015 psia
Probe diameter 12 mm/0.5 in 12 mm/0.5 in 12 mm/0.5 in 12 mm/0.5 in
Installation Flange 36 mm/1.4 in Fitting body M22 x 1.5
Fitting body NPT 1/2 in
Fitting body R 3/8 in ISO
Fitting body G 1/2 in ISO
Fitting body NPT 1/2 in
Fitting body R1/2 in ISO
Fitting body NPT 1/2 in
Ball-valve set BALLVALVE-1
Sampling cell HMP302SC DMT242SC or DMT242SC2
Measurement Performance
Dew Point
Sensor Vaisala DRYCAP 180M
Measurement range -70 … +80 °C (-94 … +176 °F) Td
Measurement range for continuous use -70 … +45 °C (-94 … +113 °F) Td
Accuracy up to 20 bar/290 psia ±2 °C/±3.6 °F (see the accuracy graph below)
Accuracy, 20 … 50 bar/290 … 725 psia Additional inaccuracy +1 °C Td
Dew Point Accuracy vs. Measurement Conditions
Response time 63% [90%] at +20 °C gas temperature
T63 [T90] response times at 20 °C and 1 l/min flow:
-60 … -20 °C Td (-76 … -4 °F Td) 5 s [10 s]
-20 … -60 °C Td (-4 … -76 °F Td) 45 s [10 min]
Measurement range 0 … +80 °C (+32 … +176 °F)
Accuracy ±0.2 °C at room temperature
Temperature sensor Pt100 RTD Class F0.1 IEC 60751
Relative Humidity
Measurement range 0 … 70 %RH
Accuracy (RH <10 %RH, at + 20 °C) ±0.004 %RH + 20% of reading
Concentration by Volume (ppm)
Measurement range (typical) 10 … 2500 ppm
Accuracy (at + 20 °C, 1 bar) 1 ppm + 20% of reading
Other measurement parameters available (model-dependent): mixing ratio, absolute humidity, pressure dew point calculated to 1 bar, temperature difference (T-Td), water vapor pressure
Operating Environment
Operating temperature for probes -40 … +80 °C (-40 … +176 °F)
Mechanical durability Up to +180 °C (+356 °F)
Mechanical durability of transmitter
40 … +60 °C (-40 … +140 °F)
Mechanical durability with display 0 … +60 °C (+32 … +140 °F)
Storage temperature range -55 … +80 °C (-67 … +176 °F)
Pressure range for probes See probe specifications
Sample flow rate No effect
Measured gases Non-corrosive gases
Electromagnetic compatibility Complies with EMC standard EN61326-1, Industrial environment
Note: Transmitter with display test impedance of 40 Ω is used in IEC61000-4-5 (Surge immunity)
Inputs & Outputs
Operating voltage 10 … 35 VDC, 24 VAC ±20 %
with optional power supply module 100 … 240 VAC 50/60 Hz
Power Consumption at 20 °C (Uin 24VDC)
RS-232 Max. 25 mA
Uout 2 x 0 … 1V / 0 … 5 V / 0 … 10 V Max. 25 mA
Iout 2 x 0 … 20 mA Max. 60 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
Temperature dependence of the analog
± 0.005 %/°C full scale
External Loads
Current outputs RL < 500 Ω
0 … 1 V output RL > 2 kΩ
0 … 5 V and 0 … 10V outputs RL > 10 kΩ
Wire size 0.5 … 2.5 mm2 (AWG 20 … 14)
stranded wires recommended
Digital outputs RS-232, RS-485 (optional)
Protocols ASCII commands, Modbus RTU
Service connection RS-232, USB
Relay outputs 0.5 A, 250 VAC, SPDT (optional)
Ethernet Interface (Optional)
Supported standards 10BASE-T, 100BASE-TX
Connector 8P8C (RJ45)
IPv4 address assignment DHCP (automatic), static
Protocols Telnet, Modbus TCP/IP
Optional Data Logger with Real-time Clock
Logged parameters Max. three with trend/min./max.values
Logging interval 10 sec (fixed)
Max. logging period with max. temporal resolution 4 years, 5 months
Logged points 13.7 million points per parameter
Battery lifetime Min. 5 years
Display LCD with backlight, graphical trend
display of any parameter
Menu languages English, Chinese, Finnish, French,
German, Japanese, Russian, Spanish,
Mechanical Specifications
Cable bushing M20x1.5 for cable diameter 8 … 11 mm/ 0.31 … 0.43 in
Conduit fitting 1/2″ NPT
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 219685
Probe cable diameter 5.5 mm (0.22 in)
Standard probe cable lengths 2 m, 5 m, or 10 m (6.6 ft, 16 ft, or 33 ft)
(Additional cable lengths available, see order forms for details)
Housing material G-AlSi 10 Mg (DIN 1725)
Housing classification IP66
IP65 (NEMA4X) with local display
Weight (depending on selected probe, cable, and modules) 1.0 … 3.0 kg (2.2 … 6.6 lb)


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