Vaisala HUMICAP® Technology

A man in a greenhouse taking care of plants

Until the early 1970s, hair hygrometers were common and at that time, reliable humidity measurement was an unresolved challenge. To solve this, Vaisala began developing a new type of humidity sensor using semiconductors and thin-film materials. 

In 1973, Vaisala introduced HUMICAP®, the world’s first thin-film capacitive humidity sensor at CIMO VI congress. HUMICAP was a radical innovation that changed humidity measurements for good. The new technology was groundbreaking: the sensor had no moving parts, and due to the advanced use of semiconductor and thin-film technologies, it was amazingly small. Since then, Vaisala has become 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.

How it works

HUMICAP is a capacitive thin-film polymer sensor consisting of a substrate on which a thin film of polymer is deposited between two conductive electrodes. The sensing surface is coated with a porous metal electrode to protect it from contamination and exposure to condensation. The substrate is typically glass or ceramic. The thin-film polymer either absorbs or releases water vapor as the relative humidity of the ambient air rises or falls. The dielectric properties of the polymer film depend on the amount of absorbed water. As the relative humidity around the sensor changes, the dielectric properties of the polymer film change, and so does the capacitance of the sensor. The instrument’s electronics measure the capacitance of the sensor and convert it into a humidity reading.


Vaisala Humicap Sensor structure in a picture


Typical applications for humidity measurement

Vaisala’s humidity instruments with HUMICAP sensors are suitable for a wide range of applications. From power and steel to life sciences and building automation, many industries need to measure humidity – here are just a few: Humidity must be measured and controlled in many drying processes, such as those in construction material and paper manufacturing, and fluid bed dryers. The humidity of the process air is a good indicator of the progression of the drying process.

Cleanrooms and other critical environments also require high-performance environmental measurements in order to operate consistently and within specifications. In addition, glove boxes and isolators – used for handling moisture or gas-sensitive materials – benefit from accurate and reliable humidity measurements. Measuring humidity in a critical environment can be especially challenging. In the food industry the dryers and ovens used in bread baking and cereal manufacture require a carefully controlled humidity level to maintain consistent quality and high yield, and to give distinctive characteristics to the finished product. In building automation, optimizing both the temperature and relative humidity of the indoor environment enables a greater level of comfort for occupants than optimizing temperature alone. Careful humidity control is a must in museums and archives, warehouses, and other environments where humidity-sensitive materials are stored.

Visitors at the art museum


Vaisala HUMICAP humidity products

Despite the fact that the HUMICAP innovation was originally designed for a new type of a radiosonde, the greatest interest came from elsewhere: people working in diverse environments.The need for reliable humidity measurement was common to all, and instruments that could do this accurately were few and far between.

Today we offer everything you need for measuring humidity, with a wide range of humidity instruments covering applications from HVAC to the most demanding industrial applications, both indoors and outdoors, and also on planet Mars. Vaisala’s humidity instrument offering includes transmitters, modules for volume applications, portable and handheld humidity meters, and humidity calibrators. 

Read more about HUMICAP's journey to planet Mars.

Women working at the laboratory


HUMICAP’s unique benefits
Excellent long-term stability
Insensitive to dust and most chemicals
Chemical purge option for stable measurements in environments with high concentrations of chemicals
Sensor heating for measurements even in condensing environments
Full recovery from condensation





for relative humidity, temperature and dew point applications
Vaisala offers a wide range of OEM modules for relative humidity (RH), temperature (T)...
HMM100 modules

Humidity Module HMM100

for environmental chambers
The Vaisala HUMICAP® Humidity Module HMM100 is an open frame module for integration into environmental chambers. The...

Sensor Information

Vaisala INTERCAP® is an interchangeable general purpose humidity sensor with good humidity durability and short response time.
Vaisala HUMICAP® 180C is a composite general purpose humidity sensor with integral Pt100 sensor. It has good humidity durability and short response time. The item contains humidity and temperature sensors. This sensor is used for chemical purge and heated probe options.
Vaisala HUMICAP® 180R is a robust general purpose humidity sensor. It has high humidity durability, good long term stability and good tolerance against chemical exposure.
Vaisala HUMICAP® 180RC is a robust composite general purpose humidity sensor. It has high humidity durability, good long term stability and good tolerance against chemical exposure. The item contains humidity and temperature sensors. This sensor is used for chemical purge and heated probe options.
Vaisala HUMICAP® 180L2 is a moisture measurement sensor in liquids. It has good tolerance against chemicals and moderate humidity durability.
Vaisala HUMICAP® H3K is a 47 pF general purpose humidity sensor that is used in some older products.
Vaisala HUMICAP® R2 is the latest generation industrial humidity sensor. Compared to HUMICAP® 180R it has improved corrosion resistance.
Vaisala HUMICAP® 180V is a humidity sensor with a catalytic surface for use in processes with H2O2.
Vaisala HUMICAP® 180VC is a composite humidity sensor with catalytic surface for use in processes with H2O2.

  Spare Part Item Identification Character Integral Pt100 Temperature Sensor Encapsulation Type
Vaisala INTERCAP® 15778HM I   Type C
Vaisala INTERCAP® 10 pieces INTERCAPSET-10PCS I   Type C
Vaisala HUMICAP® 180 - discontinued 15778HM I   Type C
Vaisala HUMICAP® 180C 229011SP I X Type C
Vaisala HUMICAP® 180R HUMICAP180R R   Type C
Vaisala HUMICAP® 180RC HUMICAP180RC R X Type C
Vaisala HUMICAP® 180L2 HUMICAP180L2 L   Type C
Vaisala HUMICAP® H3 - discontinued HUMICAPK H   Type C
Vaisala HUMICAP® R2 HUMICAPR2 R2   Type D
Vaisala HUMICAP® 180V HUMICAP180V V   Type D
Vaisala HUMICAP® 180VC HUMICAP180VC C X Type D
NOTE: After the latest sensor update the INTERCAP® sensor has been upgraded to the same environmental tolerance as the old HUMICAP® 180. Please use spare part item 15778HM for products using the HUMICAP® 180 sensor.


  • All materials comply with UL V-0.
  • Thin film capacitor structure on glass substrate (Type C) or alumina (Type D).
  • Sensor frame is made of lubricated 30% glass reinforced LCP resin (white LCP Zenite 6130L).
  • Sensor pins are copper alloy with electroplated gold coating.
  • Sensor chip is attached to pins using silver-filled epoxy glue.
  • Glue is protected with white thermal curing marking ink.

See attachment for mechanical dimensions.
See Intercap Sensor replacement instructions, example product HMP60. Instructions are generic and work for other products, too.