How Humidity Sensors are Used in Wood Dry Kilns
Wood products are everywhere from the paper receipt we received at the grocery store to the framing of our houses. Converting a tree into these products takes a considerable amount of processing. Many of these processes – above all drying the wood in wood dry kilns - require harsh environments that must be accurately monitored.
From a Forest to a House
Sawmills are the first stop the tree makes after being cut in the forest. Saws reduce the large round shape to smaller rectangular planks, called green wood. Eventually these planks will make their way into the structure of a building.
In the forest, trees soak up water and other nutrients and distribute them throughout the trunk. This means that the green wood is heavily saturated with water. This water content makes green wood dimensionally larger than dry wood – just like how a sponge is larger when wet than when it is dry. As wood dries, it shrinks. If a building were constructed with green wood then, over time, the dimensions of the structure would change as the wood dries. It would become unstable and potentially collapse.
To prevent these issues, excess moisture is removed using large wood dry kilns. During this process, green wood boards are stacked into the kiln. Inside the wood dry kiln hot air circulates for many hours. As the wood heats up moisture is released in the form of steam. This increases the humidity of the kiln, which is measured with a humidity and temperature sensor.
Measuring the Quality of the Process in Wood Dry Kilns
E+E Elektronik humidity and temperature sensors are installed onto the walls of wood dry kilns to provide measurement readings. Over time, the moisture content in the wood decreases and the overall humidity in the air decreasing as a result. These sensors indicate when the wood is sufficiently dry and ready to be removed from the wood dry kiln.
This process can cause issues with a sensor. Along with water, other compounds such as acid and volatile oils can evaporate out of the wood. These accumulate onto the sensor as residue and affect the accuracy of the readings, known as drift.
Ensuring Longevity and Accuracy
E+E Elektronik sensors are designed to operate in wood dry kilns and ensure accurate readings over time. In particular these include:
- A polycarbonate transmitter housing rated to IP65 to ensure moisture stays out of the enclosure,
- Stainless steel probe bodies to survive the high heat and humidity,
- Detachable sensor probes that can be easily cleaned and calibrated, and
- E+E’s proprietary sensor coating to ensure that critical elements are not infiltrated by residues.
E+E Elektronik will handle the toughest environments, making it an ideal choice for wood dry kiln applications.