Yes, I know no one can see how much water vapor is present in the air but you can measure it by yourself using a portable device called a hygrometer. If this sounds interesting to you, this article will surely surprise you. So, read on. Though today you can see various upgraded models of hygrometers in the market, the first-ever design of the same was given by Leonardo da Vinci in the s. Below are its image and a brief idea behind it. As you can see, Leonardo da Vinci created a simple yet clever design wherein two absorbent and non-absorbent materials were fixed around a gauge.
Now, as the humidity in the air increases, due to its absorbing power, the absorbent material will get saturated with moisture and become heavy. This difference in weight of the absorbent and non-absorbent material was then used to determine the relative humidity in the air.
In this model of hygrometer, he suspended the hair strand on the device at a certain tension. While doing so, the hair strand will move across the graduated scale to determine the humidity in the air. Read on to know how it works. A psychrometer uses two thermometers:. Just like other instruments used for measuring humidity, hygrometers work by relying on other quantities or measurements of temperature, mass, and pressure among others as these things absorb moisture.
Hygrometers are considered weather instruments that can measure humidity. It was in the s when one of the very first models of hygrometers appeared. Leonardo da Vinci constructed his early version of this device in which his goal was to measure the moisture in the air. He had a genuinely clever design, which centered around a gauge that had absorbent and non-absorbent materials on each side.
Whenever humidity would increase, the side with the absorbent material would get heavier as it got more saturated. The weight difference was interpreted as a reading for a relative humidity.
Just like what da Vinci developed, the device measured humidity. The difference though is that de Saussure used a strand of hair, which was suspended on the device under tension.
The moisture in the air had an effect on the hair, causing it to either contract or expand, depending on the humidity level. A needle would point to a number on the dial, which he interpreted as the humidity in the air. Other versions of the device were created.
Most of the early designed replicated thermometer technology during that time. To be specific, the devices borrowed the techniques used in wet and dry bulb psychrometer.
It had two mercury thermometers, which as the name implies, had one dry and one wet. The latter had a wet fabric sleeve covering it at the base of the device.
To measure relative humidity, the difference in the temperatures of the dry and wet thermometers was calculated. Today, there are different types of a hygrometer and how they work will depend on their design. For instance, one of the types is a capacitive hygrometer. Devices classified under this form use different other types of sensors. Capacitive hygrometers are created for applications where price, fragility, or space is a concern, so they risk the accuracy of reading moisture for the affordability of the device.
Capacitive hygrometers measure the effect of moisture on a metal oxide material. If not calibrated, the accuracy is up to three times worse. The sensors though can withstand high temperatures and the effects of condensation, and they are suitable for various applications.
However, these capacity hygrometers have sensors that can easily be contaminated and show signs of aging rapidly. Another sensor is resistive, which is less sensitive when compared to capacitive sensors. Since they are not as sensitive as capacitive, resistive sensors require a more complex circuit board. The material also dictates how robust the hygrometer will be against condensation. Hygrometers are deemed as useful tools, which utilize calculation and calibration of pressure and temperature changes.
This can take at least four hours on a 50mm thick screed where the damp proof membrane is placed between the base and the screed, and considerably longer for thicker floor constructions. The readings from the hygrometer should inform the next steps taken. Excess subfloor moisture is one of the most common causes of floor failure, but it can be avoided by installing a waterproof surface membrane to impede the passage of rising damp or residual construction moisture.
There are a number of options available should protection against excess moisture be required.
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