One morning, I noticed water coming from the hanging lamp, which was not a good thing. We had a plumber deal with the leak, and later, the insurance company sent a restoration crew to check out the damage. Although this was all rather distressing, I was intrigued with their handheld moisture sensors and wondered how they worked.
Initially, they used infrared cameras to quickly see where the moisture problems are. These devices detect infrared energy, convert it into electronic signals and display the results with different colours corresponding to temperature. Wet areas tend to have a cooler temperature than dry because of evaporative cooling, which is what sweat is all about. At the infrared camera exhibit in the Eureka! gallery at TELUS World of Science, people are usually more interested in seeing how warm their faces look.
The restoration workers also used sensors that they touched to the surface—noninvasive, pinless, moisture meters. These send out a radio frequency signal and take a measurement of how the signal is affected. More moisture in the material results in a higher reading. The reading for gypsum in drywall depends on the density and other properties, so they measured a separate wall for a reference. Apparently, studs can distort the result, so they tried it out in different places.
They marked off the areas to be treated and came back with a bunch of big fans and dehumidifiers that we had to leave running for a few days, which did not make my dog happy.
When the restorers came back, they tested for moisture with pin meters. This sensor had two sharp pins, which the worker repeatedly stuck into the drywall. It measured the electrical conductivity of the material between the pins. A higher reading means more moisture. This is supposed to be more precise. The restorers left lots of tiny holes in the affected area, which were eventually covered up by a plasterer.
I came across a number of sites that compared the pros and cons of these different devices, mostly between pin and pinless meters. Many of them seemed to be directed at carpenters for assessing the moisture content of the wood they were using. The restorers seemed to use them all, but for slightly different purposes. Initially they were going for quick assessments and then later for greater precision.
I hope you do not have the same reason as I did to wonder about moisture meters. But if you do know about them, please share your insights in the comments.
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