Vaisala HUMICAP® Celebrates Its 40 Years

In the early 1970s, humidity was measured using organic materials, such as human or animal hair, in hygrometers. At the time there were few alternatives available and the accuracy and reliability issues of such measurement methods were well known. In an effort to find a solution, Vaisala contracted the semiconductor laboratory of the Technical Research Center of Finland to cooperate on the development of sensors. As a result of this work, Vaisala introduced HUMICAP®, the world’s first thin-film capacitive humidity sensor in 1973.

As the world’s first thin-film capacitive humidity sensor, the HUMICAP® was a radical innovation that completely changed the way humidity is measured. The new ground-breaking technology had no moving parts, and it was amazingly small due to the advanced use of thin-film technology.

The innovation was originally designed for a new radiosonde; however the greatest interest for this revolutionary new sensor came from various industrial customers. Continuous innovation of the sensor has developed INTERCAP®, an interchangeable humidity sensor, as well as HUMICAP® variant which measures moisture in oil. The fourth generation humidity sensor with improved stability and chemical tolerance was introduced in 2006.

Nowadays, products based on Vaisala HUMICAP® technology range from radiosondes to hand-held meters and industrial transmitters. The sensor is manufactured in-house from start to finish in state-of-the-art cleanroom facilities at Vaisala and it covers applications from HVAC to the most demanding industrial and environ-mental applications, both indoors and out.

Today, Vaisala is the market leader in relative humidity measurements, and thin-film capacitive humidity sensors have developed from one company’s innovation into a global industry standard.