What is a Low Range Dew Point Analyzer?
Measuring the dew points of pure gases such as nitrogen, argon, and hydrogen cannot be done using a calculation based on relative humidity and temperature. This is because the dew points are so low (typically from -20°F to -120°F, or -28.9°C to -84.4°C) that even the slightest error in relative humidity measurement can have a significant impact on the calculated dew point. With gases this dry, moisture levels are measured using a more direct measurement.
Since ambient dew point levels will quickly saturate a sensor that is designed to measure only trace amounts of moisture, it can sometimes take a long time for a low range dew point sensor to dry out enough to provide an accurate reading. For this reason, the sensor in Super Systems’ portable low range dew point analyzer (DPL4000) has a self-heating tip to reduce the measurement time to a few minutes instead of a few hours. The permanently mounted low range dew point analyzer (DPC3500) does not require this feature since it is typically mounted in the gas stream and is constantly surrounded by dry gas.
For pure gases, the dew point measurement can provide information regarding the purity of the gas, with a lower dew point indicating higher purity levels.