DMT345 and DMT346 Dewpoint Transmitters for High Temperature Applications

The Vaisala DRYCAP® Dewpoint Transmitters DMT345 and DMT346 are designed for humidity measurement in industrial drying applications with particularly high temperatures.

  • The DMT345 measures humidity at temperatures up to 180°C (+356 °F)
  • The DMT346 measures humidity at temperatures up to 350 °C (+662 °F)
  • Unique auto-calibration
  • Vaisala DRYCAP® Sensor provides accurate, reliable measurement with excellent long-term stability and fast response time
  • Condensation-resistant
  • Graphical display with keypad for convenient operation
  • Optional mains power supply module and alarm relays
  • Integrated data logging, with over four years of measurement history
  • LAN and WLAN communication options
  • NIST traceable calibration (certificate included)
 DMT345 and DMT346 Dewpoint Transmitters for High Temperature Applications 

DMT345 and DMT346 Dewpoint Transmitters for High Temperature Applications 




Operating Principle

DRYCAP’s unrivalled performance is based on two innovations: the proven capacitive thin-film polymer sensor and the auto-calibration function. The sensor’s thin-film polymer absorbs or releases water vapor as the surrounding humidity  increases or decreases. 

The dielectric properties of the polymer change as the humidity around the sensor changes, as does the capacitance of the sensor. Capacitance is converted into a humidity reading. The capacitive polymer sensor is bonded together with a temperature sensor, and dew point is calculated from the humidity and temperature readings. 

Vaisala’s patented auto-calibration function optimizes the measurement stability at low dew points. The sensor is heated at regular intervals during the automated auto-calibration procedure. 

The humidity and temperature readings are monitored as the sensor cools to ambient temperature, with offset correction compensating for any potential drift. This enables the DRYCAP sensor to deliver accurate measurements in the long term, dramatically reducing the need for maintenance.