Humidity measurement of air is carried out in order to record specific values of moisture content. The importance of moisture in the fields of industry, biology and medicine has increased with time. In many manufacturing processes, the humidity of air can exert a decisive influence on the quality of its’ products. Continuous monitoring of humidity is therefore an important factor in industrial production. Compressed air drying and dewpoint measurement may be differing areas of technology but many aspects of process and measurement technology are frequently closely interlinked. Adsorption drying and dewpoint measurement complement each other ideally. In the increasingly widespread use of adsorption dryers, dewpoint measurement technology will improve monitoring, economy, operating safety and reliability.
Dealing with compressed or dried air is subject to conflicting points of view. On one hand, high humidity must be avoided in all cases, yet the air must be dried only so far that its absolute humidity affects neither systems nor product quality. A low moisture content in air is acquired at the price of high operating costs. Endeavouring to adapt the dewpoint to the manufacturing process is an optimum compromise. Manufacturers of the pure gases or plastics granules as well as intermediate products must offer guarantees for the product quality linked to moisture content against the background of ever more stringent quality and product liability requirements.
Many plastics, such as polyester or modified polycarbonate, must not be processed if the moisture content is more than 0.01%. Most dryers, therefore, operate with a safety margin in order to keep within guaranteed residual moisture contents. Improved dryer performances, more precisely specified product characteristics and ecological points of view are determining factors when controlling moisture. Next to avoiding too high an air humidity, the avoidance of too low air humidity has also become important. If, for instance, the previously mentioned polycarbonates show too high a level of dessiccation, they lose qualities such as insulation or surface lustre. Too high a level of drying also leads to colour changes or material brittleness.
