will show absorption in the wavelengths that correspond to the molecular structure of the condensation formed. In this way, the device is able to distinguish between water condensation and other types of condensates, such as, for example, hydrocarbons when the gaseous media is natural gas. One advantage of this method is its relative immunity to contaminants thanks to the inert nature of the transparent material. Similar to a true chilled-mirror device, this type of analyzer can accurately measure the condensation temperature of potential liquids in a gaseous medium, but is not capable of measuring the actual water dew point as this requires the accurate measurement of the evaporation temperature as well. Electrolytic The electrolytic sensor uses two closely spaced, parallel windings coated with a thin film of phosphorus pentoxide (P2O5). As this coating absorbs incoming water vapor, an electrical potential is applied to the windings that electrolyze the water to hydrogen and oxygen. The current consumed by the electrolysis determines the mass of water vapor entering the sensor. The flow rate and pressure of the incoming sample must be controlled precisely to maintain a standard sample mass flow rate into the sensor. The method is fairly inexpensive and can be used effectively in pure gas streams where response rates are not critical. Contamination from oils, liquids or glycols on the windings will cause drift in the readings and damage to the sensor. The sensor cannot react to sudden changes in moisture, i.e., the reaction on the windings’ surfaces takes some time to stabilize. Large amounts of water in the pipeline (called slugs) will wet the surface and require tens of minutes or hours to “dry-down.” Effective sample conditioning and removal of liquids are essential when using an electrolytic sensor. Piezoelectric sorption The piezoelectric sorption instrument compares the changes in the frequency of hygroscopic coated quartz oscillators. As the mass of the crystal changes due to the adsorption of water vapor, the frequency of the oscillator changes. The sensor is a relative measurement, so an integrated calibration system with desiccant dryers, permeations tubes and sample line switching is used frequently to correlate the system. The system has succeeded in many applications, including natural gas. It is possible to have interference from glycol, methanol, and damage from the hydrogen sulfide, which can result in erratic readings. The sensor itself is relatively inexpensive and very precise. The required calibration system is not as