DSS70A Portable Sampling System and Sampling Cells for DM70

The Vaisala DRYCAP® Portable Sampling System provides a compact solution for field checking dew point where direct measurement is difficult.

Typical applications for the sampling system are metal treatment and plastics drying processes.

  • A compact solution for sampling from hot or dirty processes
  • Enables measurement from both pressurized processes and processes at atmospheric pressure
  • Vaisala DRYCAP® sensor with patented autocalibration function
  • Low maintenance need due to excellent long-term stability
  • NIST traceable (certificate included)
DSS70A Portable Sampling System and Sampling Cells for DM70 

DSS70A Portable Sampling System and Sampling Cells for DM70 

Product Information

DSS70A Portable Sampling System

The DSS70A is designed to provide dew point sampling flexibility for the DM70 hand-held dew point meter. For processes at atmospheric pressure, a battery powered pump is used to extract a gas sample. For pressurized processes up to 20 bar, the sample is measured at process pressure and then reduced to atmospheric pressure for venting or re-direction, bypassing the pump. In all cases, the sample gas passes through a filter to remove particulate contamination before measurement. Flow through the system is controlled and monitored with a needle valve and flow meter.

The DSS70A is easily connected to an appropriate sample point with tubing (typically 1/4” or 6 mm). The measured dew point must be below ambient temperature to avoid condensation in the system. Gas temperatures higher than +40 °C (+104 °F) should be cooled with a short PTFE (included in the DSS70A system) or stainless steel tube prior to entering the DSS70A. DSS70A is an accessory for DM70 Dewpoint Handheld Meter.

Sampling Cells for Pressurized Processes

The DM70 can easily be connected to pressurized processes. In addition to direct pipeline installation, a variety of sampling cell options are available for gas sampling.

The DSC74 sampling cell is the recommended choice. It has a variety of connection adapters that allow several different ways of installation. The quick connector with a leak screw allows a very fast connection for compressed air lines. Additionally, two thread adapters are available for the inlet port. The DSC74B is a two-pressure sampling cell, which enables measurements in both process and ambient pressure. This sampling cell is especially suitable for dew point measurements in SF6 gas with the DMP74C probe.

The DMT242SC is a basic sampling cell. The DMT242SC2 is a sampling cell supplied with welded Swagelok connectors for sampling in a 1/4” pipeline.

Operating Principle

RYCAP’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.