selection guide

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how to test wood moisture

Although the weighing method (difference between weight before and after drying process) is the only worldwide recognized reference method for the exact measurement of moisture, many good instruments (but even more easy-to-use, faster and less intrusive) are today available on the market for most of applications.


The most important thing is, first of all, to choose the right instrument, according to customer's needs, as different needs can only be satisfied with different instruments. Buying an instrument without having analyzed the pros and the cons may often lead to the wrong purchase and to customer's disappointment.
Many meters are available today on the market and can be divided into two main groups: contact meters (which measure the dielectric characteristics of wood) and pin type meters (which measure the resistance between two electrodes).

Contact meters or pin type meters?

Contact meters can make readings in depth, due to the generated electric field. The reading depth depends on the characteristics of the instrument. The obtained value is an average of measured moisture value, which is calculated with decreasing sensitivity at the increase of depth.
Pin type meters are used to measure the electric resistance between two electrodes. The reading is made only on the space between the two electrodes at the depth where they have been inserted. The measured value corresponds to the maximum moisture between the electrodes, both on surface and in depth. If the highest moisture is in the middle, you can easily know moisture distribution into the board simply by noticing the reading changes on the instrument when electrodes are placed. Otherwise, the only other way to get this information is by using insulated electrodes, with unshielded ends, to avoid the influence of surface layers on readings.

Contact meters are better...

  • If the material to be measured has humidity below 8-10%

  • If it is essential, do not cause any damage to the material to be measured

  • If the surface of the wood has been wet with frost

  • If you want to make numerous measurements in a short time

Drilling instruments measure the electrical resistance between two electrodes; the measurement is carried out only in the space between the electrodes, at their insertion depth. The measured value corresponds to the maximum humidity found between the electrodes, whether on the surface or in depth. If the wettest area is the central one, it is easy to obtain an indication of the humidity distribution inside the axis, observing the variation in the instrument indication during the insertion of the electrodes; otherwise, the only way to obtain this information is to use insulated electrodes, with only the tips uncovered, in order to exclude the influence of the surface layers.

Pin type meters are better...

  • If the material to be measured has humidity above 20-30%

  • If the material to be measured is less than 2 cm thick and it is not possible to overlap several layers without air gaps

  • If you suspect that moisture is not evenly distributed

  • If the measurement speed and material damage are secondary to the required accuracy

  • From the operating principle it is evident that the only condition in which the measurements obtained with the two types of instrument are comparable is with seasoned or dried timber, having a uniform distribution of humidity inside.

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Precision

The LogicaH & S instruments have been calibrated on stable reference samples, made on the basis of measurements made on wood of various species, whose humidity has been verified according to the UNI 9091-2 / 87 standard (weighing method). Other timbers were classified by analogy with the tested samples. Given the non-homogeneous nature of the wood, the performance of the instruments cannot be automatically ensured on samples other than those tested, even if they belong to the same species. For this reason, LogicaH & S, upon customer request, is able to provide the tools complete with a Verification Certificate carried out directly on the customer's timber, drawn up by CATAS SpA (accredited testing laboratory). See the FAQ page for more information on this topic.

Whatever your need, with a Logica H&S instrument you will have a reliable and precise work partner, strictly MADE IN ITALY.

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