Measuring the dew point plays an important role in many industrial applications. Whether in compressed air systems, in building technology or in drying - the quality of all moisture-sensitive processes depends on the reliable monitoring of the dew point temperature by dew point sensors. Regular calibration is required to ensure the accuracy of these sensors. The dew point calibration system in the E+E Elektronik calibration laboratory is characterized by a very low measurement uncertainty and a calibration range from -90 °C frost point (tf) to +95 °C dew point (td). And: E+E Elektronik's calibration laboratory is one of the few institutions in the world that can also calibrate dew point mirror hygrometers with high accuracy.

The dew point as an important process variable

The dew point is an important instrument for controlling and optimizing processes in various areas, for ensuring product quality and for preventing moisture damage. For several reasons:

• Prevention of condensation: in processes where air or gases are cooled, it is important to avoid condensation, as this can lead to corrosion, damage to equipment and impairment of product quality.
• Quality control: In many production processes, such as in the food, pharmaceutical and electronics industries, humidity control is crucial for the quality and shelf life of products.
• Energy efficiency: In air conditioning and ventilation technology as well as in process cooling, monitoring the dew point helps to maximize the efficiency of cooling systems. This ensures that cooling is effective without wasting energy unnecessarily.
• Optimization of drying processes: In industries such as paper manufacturing, textiles and construction, drying is an important process. Monitoring the dew point helps to speed up the drying process and save energy.
• Protecting electronics: When manufacturing and storing electronics, it is important to avoid condensation, which can lead to short circuits and failures.

There are various methods for measuring the dew point. Either the dew point temperature is measured directly - this is done using dew point mirror hygrometers or metal oxide sensors. In addition, the dew point can be calculated using humidity and temperature measurement. The dew point sensors from E+E Elektronik work according to this principle.

Dew point mirror calibration at E+E Elektronik

Dew point measuring devices are often calibrated with the aid of a dew point mirror, as this provides very accurate values due to its physical measuring principle. Dew point mirror hygrometers are mostly used as reference devices in measuring laboratories or in production facilities.

Of course, dew point mirror hygrometers also need to be calibrated. There are currently only a few calibration facilities worldwide that offer dew point mirror calibration. One of these is the calibration laboratory of E+E-Elektronik. This is of particular interest to accredited calibration laboratories and other DIs or NMIs.

The E+E dew point calibration system is characterized by a very low measurement uncertainty (from 20 mK) and a calibration range from -90 °C frost point (tf) to +95 °C dew point (td). Calibration is performed in nitrogen as standard. On request, dew point hygrometers can also be calibrated in other carrier gases such as methane.

Calibration procedure

In a 2-pressure humidity generator, a gas flow is completely saturated at a defined pressure and temperature. This is fed to the test specimen, where it generates a defined dew point temperature depending on the pressure.

Optionally, the test specimen can be temperature-stabilized in a measuring chamber. The calibration system is the Austrian national standard for humidity.