DMT340 Series Dewpoint and Temperature Transmitters for Very Dry Conditions

The Vaisala DRYCAP® Dewpoint and Temperature Transmitter Series DMT340 is designed for industrial low humidity applications.

Typical applications include compressed air drying and metal treatment.

  • Five different probe types designed to meet various installation requirements
  • Vaisala DRYCAP® Sensor provides accurate, reliable measurement with excellent long-term stability and fast response time
  • Condensation-resistant
  • Unique auto-calibration feature
  • Graphical display and keypad for convenient operation
  • Optional alarm relays and mains power supply module
  • Integrated data logging with over four years of measurement history
  • LAN and WLAN communication options
  • NIST traceable calibration (certificate included)
 DMT340 Series Dewpoint and Temperature Transmitters for Very Dry Conditions

DMT340 Series Dewpoint and Temperature Transmitters for Very Dry Conditions




Operating Principle

DRYCAP’s unrivaled 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.