Precise Dew Point Measurement at Low Humidity WHITEPAPER Precise dew and frost point measurement at very low humidity is essential in industries such as semiconductor manufacturing, gas analytics, cleanrooms, compressed air systems, and battery production, where minimal moisture can compromize product quality and process stability. Because dew point depends on temperature and pressure, concepts such as pressure dew point and the distinction between dew and frost point below 0 °C are critical for accurate interpretation. Achieving reliable measurements at these levels is challenging, as sensors must detect tiny amounts of water vapor with high sensitivity, remain stable over long periods, and withstand condensation and chemically aggressive environments. Innovative Sensor Technology IST AG addresses these challenges with capacitive polymer-based humidity sensors and HYT modules that offer high sensitivity, excellent long term stability, and strong condensation and chemical resistance suitable for dew point applications below -60 °C, providing fully calibrated and temperature compensated digital outputs, pressure-tight designs, and customization options for seamless industrial integration.

1.0 Fundamentals on Dew Point 2.0 Dew Point Measurement Applications 3.0 Challenges in Low Humidity Measurement 4.0 iST Sensor Solutions 5.0 About iST Measuring the dew point at extremely low humidity levels is a key challenge in many industrial applications – from semiconductor manufacturing and gas analytics to process air monitoring. iST offers high-precision sensor solutions specifically designed to meet these demanding requirements. 1.0 Fundamentals on Dew Point Dew point is the temperature at which air becomes saturated with water vapor, causing condensation to start. At this point, the...

Ultra-dry environments, such as battery manufactuing (right), or industrial air compressors in factory air supply sytems (below) , are highly dependent on reliable dew point monitoring. 2.0 Dew Point Measurement Applications Dew point monitoring is essential in numerous industrial and technological processes where low levels of humidity need to be measured to ensure quality, safety, and efficiency. Typical applications include: • • • • • • • • • • Compressed air monitoring in HVAC systems: Preventing condensation and corrosion in air distribution networks Drying processes: Controlling moisture...

3.0 Challenges in Low Humidity Monitoring As dew point is typically important for low humidity applications, there are numerous challenges for accurate dew point measurements. At extremely low humidity levels, the water vapor content is minimal, which means sensors must be exceptionally sensitive to detect even the smallest traces of humidity. Long-term stability is another critical factor, as instruments are often deployed in continuous operation for years. Any drift in measurement can lead to costly process deviations. In addition to sensitivity and stability, dew point sensors must withstand...

By measuring temperature and relative humidity, the module provides the necessary data to compute the dew/ frost point Td/f . As an easy approximation, the dew/frost point Td/f can be calculated using the Magnus formula as described by Sonntag [1]: and ambient temperature T in [°C] and relative humidity RH in [%RH] with constants as stated in Table 1. Because it is important to distinguish between dew point and frost point, iST recommends calculating frost point for temperatures below 0 °C. Please note that in Equation (2), the parameters over water must be applied irrespective of whether a dew...

5.0 About iST Your partner and manufacturer for physical, chemical and biological sensors With 35 years of experience iST is one of the world’s leading manufacturers of physical, chemical and biological sensors. We specialize in the development and manufacturing of temperature sensors, thermal mass flow sensors and modules, humidity sensors and modules, conductivity sensors and biosensors. In addition to our standard products, we offer sensor adaptions to individual, customer-specific application needs – right up to the joint development of new technologies. iST-sensors are characterized by their...