Relative humidity and measuring it with humidity sensors is a major factor in many areas. It influences our well-being, for example, but also the energy efficiency and safety of processes and systems, or the quality and reliability of the production process. To ensure precise monitoring and control of the moisture content, it is essential for humidity sensors to deliver exact results – even in difficult conditions. E+E Elektronik has developed a special sensor protection precisely for this use case – the proprietary E+E sensor coating.
Humidity sensors are exposed to a variety of influences depending on the application and installation location. These factors can negatively impact on the measuring performance and shorten the sensor's service life. Specific challenges for humidity sensors include:
- Dusty, dirty and oily environments
- Corrosive environments/salts (e.g., off-shore applications)
- Deposits caused by high humidity levels
When using humidity sensors in challenging environments without appropriate protective measures, deteriorating long-term stability is noticeable and an increased occurrence of stray impedances is unavoidable. The resulting change in capacitance, which is mainly attributable to deposits and conductive particles on the active sensor surface, has a considerable influence on the measurement results.
Critical Areas of Use for Humidity Sensors Include:
- Agriculture and livestock farming (stalls, breeding stations, silos, …)
- Drying chambers (wood, bricks,..)
- Mushroom farms
The lack of sensor protection can lead to problems in harsh environmental conditions. Accurate humidity measurement often relies on periodic maintenance, which needs to be carried out at shorter or longer intervals depending on the load. The work ranges from careful cleaning followed by re-calibration to inspection and calibration of the humidity sensor by the manufacturer or a calibration laboratory. The consequence is additional costs and downtime.
Protection Options for Humidity Sensors
Additional protection options, such as filter caps are available to protect humidity sensors against negative environmental influences and avoid time-consuming maintenance work. They protect the sensing head and/or sensing element against dust and other contamination. In the application, these actions can impact on the response time, however. The advantages and disadvantages of additional sensor protection therefore need to be carefully considered. Additionally, where space is at a premium, separate protection options are difficult to integrate.
The sensor coating by E+E Elektronik offers an alternative to this!
E+E Elektronik has developed a proprietary sensor coating for particularly challenging applications. This special coating has been used on E+E humidity sensing elements for years and makes a decisive difference in terms of long-term stability and service life. This is a thin, water vapour permeable layer that is applied to the neuralgic points of the sensing element (active sensor surface, leads and soldering points). It protects the sensing element against deposits and electrically conductive particles which can have a negative impact on the measurement results. At the same time, the moisture can diffuse, which allows for accurate measurement of the humidity. In this way, the sensor coating improves the measurement quality of the humidity sensing element in harsh environments. It also facilitates the design-in of the sensing element, as no additional protection options are needed.
HTE501 Humidity and Temperature Sensing Element
The proven E+E sensor coating is also used for the HTE501 humidity and temperature sensing element. The digital sensing element offers excellent measurement accuracy of ±1.8% RH (incl. hysteresis) and ±0.2 °C. The E+E sensor coating and the integrated constant current heater ensure high reliability and a long service life of the HTE501 in harsh, polluted and condensing environments.