The DRYCAP story began in the mid-1990s following an unresolved measurement challenge. Traditional humidity instruments were not accurate enough at very low humidities, while commonly used aluminum oxide sensors were prone to drift and required frequent calibration. There was a strong demand for accurate, easy-to-use, cost-effective, and low-maintenance dew point instruments.
Vaisala's solution was to combine the highest quality polymer technology with a patented key feature – auto-calibration – that would eliminate sensor drift in very dry conditions. In 1997, Vaisala introduced a a new type of dew point sensor based on thin-film polymer technology, the DRYCAP® sensor. Since its launch, the DRYCAP product family has grown to encompass a huge range of applications, from drying processes to compressed air and dry chambers. The DRYCAP sensor is particularly renowned for its reliable performance in hot and very dry environments and this highly successful innovation is still going strong today.
DRYCAP’s unrivalled performance is based on two innovations: the proven capacitive thin-film polymer sensor and the auto-calibration function. The sensor’s thin-film polymer absorbs or releases water vapor as the surrounding humidity increases or decreases. The dielectric properties of the polymer change as the humidity around the sensor changes, as does the capacitance of the sensor. Capacitance is converted into a humidity reading. The capacitive polymer sensor is bonded together with a temperature sensor, and dew point is calculated from the humidity and temperature readings. Vaisala’s patented auto-calibration function optimizes the measurement stability in dry environments. The sensor is heated at regular intervals during the automated auto-calibration procedure. The humidity and temperature readings are monitored as the sensor cools to ambient temperature, with offset correction compensating for any potential drift. This enables the DRYCAP sensor to deliver accurate measurements in the long term, dramatically reducing the need for maintenance.
Vaisala DRYCAP dew point instruments measure dew point in industrial applications, where gas humidity is typically very low. Dew point is often a critical parameter, with inadequate control resulting in problems such as process downtime, damaged process equipment, and deterioration in end-product quality. Dew point is measured in various drying and heat-treatment processes, such as plastic drying, baking ovens, and food drying. It is also controlled in compressed air, where excess moisture can result in poor end-product quality, ice formation, and equipment corrosion. Other typical applications include medical gas, dry environments in lithium battery manufacturing, and gas-insulated high-voltage equipment used in the power industry.
Vaisala's dew point instruments are suitable for accurate and stable monitoring of dry conditions in a variety of applications from -80 to +100 °C Td. Vaisala’s product range includes transmitters for demanding industrial applications, compact instruments for installation in dryers, and hand-held meters for spot checking. Portable sampling systems are also available.
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It is also controlled in compressed air, where excess moisture can result in poor end-product quality.