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Vaisala DMT345 and DMT346 Dewpoint Transmitters

Dewpoint Transmitters
DMT345 and DMT346

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 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 measurement.

Graphical display
The DMT345 and DMT346 transmitters can be ordered with a large numerical and graphical display, which allows the user to clearly monitor operational data, measurement trends and up to one-year measurement history. The optional data logger with real-time clock makes it possible to generate more than four years of the measured history and zoom in on any desired time or time frame.

Versatile outputs and (wireless) data collection.
The transmitter can be connected to a network with an optional (W)LAN interface, which enables a (wireless) Ethernet connection. For serial interface also the USB connection, RS232 and RS485 can be used. Additionally an alarm relay option is available.

The transmitter can have up to three analog outputs. Galvanic isolation of supply power and analog outputs are also offered. The recorded measurement data can be viewed on the display or transferred to a PC with Microsoft Windows® software.

Units are delivered installation-ready and meet ROHS requirements.

• 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)
• Analog outputs, WLAN/LAN

Operating Environment, both models
Mechanical durability Up to +180 °C (+356 °F) for DMT345
of probes Up to +350 °C (+662 °F) for DMT346
for 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
Inputs and outputs, both models
Operating voltage 10 ... 35 VDC, 24 VAC
with optional power supply module 100 ... 240 VAC 50/60 Hz
Default start-up time initial reading after power-up 3 s
full operation after sensor Purge and Autocal about 6 min
Power consumption @ 20 °C (Uin 24 VDC) Uout 2x0 ... 1V/0 ... 5V/0 ... 10V max 25 mA
Iout 2x0 ... 20mA max 60 mA
RS-232 max 25 mA
display and backlight + 20 mA
during sensor purge + 110 mA max
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 scal
Temperature dependence of the analog outputs ± 0.005 %/°C full scale
External loads current outputs RL< 500 ohm
0 ... 1V output RL> 2 kohm
0 ... 5V and 0 ... 10V outputs RL> 10 kohm
Max wire size 0.5 mm2 (AWG 20) stranded wires recommended
Digital outputs RS-232, RS-485 (optional)
Service connection RS-232, USB
Relay outputs 2+2 pcs (optional) 0.5 A, 250 VAC, SPDT
Ethernet interface (optional) Supported standards 10/100Base-T
Connector Connector
Protocols Telnet
Software support Vaisala MI70 link
WLAN interface (optional) Supported standards 802.11b
Antenna connector type RP-SMA
Protocols Telnet
Security WEP 64/128,WPA
Software support Vaisala MI70 link
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. three 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
Display (optional) LCD with backlight, graphic trend display
Display menu languages English, French, Spanish, Chinese, German, Japanese, Russian, Swedish, Finnish
Mechanics, both models
Cable bushing M20x1.5 For cable diameter 8 ... 11mm/0.31 ... 0.43"
Conduit fitting (optional) 1/2"NPT
User cable connector (optional) M12 series 8- pin (male)
option 1 with plug ( female) with 5 m / 16.4 ft black cable
option 2 with plug ( female) with screw terminals
USB-RJ45 Serial Connection Cable part. no 219685
Probe cable diameter 5.5 mm
Probe cable lenght 2 m, 5 m or 10 m
Housing material G-AlSi 10 Mg (DIN 1725)
Housing classification IP 65 (NEMA 4X)
Housing weight 1.2 kg


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