Moisture Measuring Devices: This Has To Be Considered Before Buying

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-06-01 01:49

Too much moisture in the surface affects the quality of a coating. The damage pattern ranges from flaking to discoloration. Moisture meters minimize these risks.

Author: Josef Schneider

When the subject of wood coating was on the curriculum in Lahr, our then industrial school teacher Klaus Packwitz told us a story. As an apprentice, his master would have instructed him to wet all the windows on the construction site early in the morning with a sponge and plenty of water. Later, the said master went through the building together with the architect to randomly measure the moisture in the windows. Unsurprisingly, the result was: "Too wet to be able to paint it." This would have given his master some air to delay the work.

Moisture meters: Large offer

There are obviously different motivations to take moisture measurements. However, one of the most important reasons is to check the surface properly. This is because excessive material moisture affects subsequent coatings.

The range of moisture measuring devices is large. The manufacturers offer a suitable device for every application. Moisture meters are basically small and handy. They weigh between 100 and 300 grams. Moisture meters fit in every work bag.

The moisture meters are powered by batteries. 9-volt block batteries are common. The information on the operating time vary. If you believe the manufacturers, this should be an average of over 30 hours. There is a greater risk that the batteries will eventually leak due to age reasons than the power will run out prematurely. Hence the tip: Check the batteries regularly and change them if necessary. Leaking batteries can damage the device.

Measuring method

There are basically two methods to measure moisture in the subsurface:

Resistance process (destructive)

Capacitive process (non-destructive)

The term "destructive" sounds worse than the process actually is. With resistance measuring devices, the user inserts two electrodes into the material to be measured - whether plaster or wood. As a rule, these are thin needles that hardly leave any traces (= destruction) in the underground. The measuring principle is simple. The wetter the material, the better the current is conducted from one electrode to the other. This measurement method is particularly suitable for soft building materials such as plaster or wood.

If the moisture measurement needs to go deeper - without damaging the surface, the capacitive method is the first choice. It measures non-destructively up to 50 millimeters deep. The moisture meter builds up an electric field and measures the capacitance. The wetter the surface, the higher the capacity.

A special form of the capacitive method is the microwave measuring method. It also works non-destructively. The penetration depth depends on the density and homogeneity of the measured material. Measurements down to a depth of 300 millimeters are possible.

If you don't want to choose either one or the other, you can use so-called combination devices.

Measuring range of the moisture measuring devices

"The subsurface must be firm, dust-free and dry", says many technical data sheets. But what is "dry"? How much moisture is acceptable? For wood, the information from the paint manufacturers is quite specific. "The moisture content in the subsurface must not exceed 15 percent," you can often read. The information on mineral substrates is less precise. Often only a look at the operating instructions for the moisture meter helps. For example, GANN mentions the following values in the instructions for the Hydromette:

Wood

dry 25-40 digits

moist 80-140 digits

Housing masonry

dry 25-40 digits

moist 100-150 digits

Basement masonry

dry 60-80 digits

moist 100-150 digits

Note at this point: The measuring range of moisture meters is often given in "digits". This is the range of the measured values. 0 to 100 or 0 to 200 digits are common. A “digit” is therefore a number step. Accordingly, the measurement tolerances in our market overview are sometimes given in percentage points, sometimes in digits.

Furnishing

Whether minimum / maximum display, hold function or illuminated display - the equipment of the devices leaves nothing to be desired. The default setting of material types is widespread. This means that the tradesman selects which substrate to measure before measuring: whether lime cement plaster, concrete, gypsum plaster or one of the stored types of wood. This function significantly increases the accuracy of the measurement results. Caravan owners among us may want to measure sandwich elements. Devices with this additional function are, however, rather rare. Likewise those with a Bluetooth interface and app connection. However, their function is extremely practical. In this way, the measurement results can be documented and sent on site. However, if a trainee has previously moistened the windows with water,these measurement results - both today and back then - are relative.

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Is the surface ready for the next step? Moisture meters create security.

Photo: Quickmix

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