{"id":27516,"date":"2024-07-12T15:11:41","date_gmt":"2024-07-12T13:11:41","guid":{"rendered":"https:\/\/www.linseis.com\/messgeraete\/additional-devices-support\/relative-humidity-l40-rh\/"},"modified":"2026-02-04T08:36:47","modified_gmt":"2026-02-04T07:36:47","slug":"l40-relative-humidity","status":"publish","type":"messgeraete","link":"https:\/\/www.linseis.com\/en\/instruments\/additional-devices-support\/l40-relative-humidity\/","title":{"rendered":"L40 HUM – Relative Humidity"},"content":{"rendered":"\t\t
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\n\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\tRelative Humidity<\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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For many applications in thermal analysis, the atmosphere plays an important role as it may affect the sample behavior or initiate reactions. Humidity influence on\u00a0building materials<\/b><\/a>, storage time of\u00a0pharmaceuticals<\/b><\/a>\u00a0and foods or influence on mechanical properties of\u00a0polymers<\/b><\/a>\u00a0are just some of the most common examples.<\/p>

Of course, the Linseis instruments are suitable for such experiments, however there is one fact that is often causing confusion and must be considered carefully:\u00a0The difference between\u00a0water vapor<\/b><\/a>\u00a0and relative humidty<\/strong>.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Difference between relative humidity and water vapor<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Relative Humidity Generators are\u00a0most commonly used for experiments around room temperature<\/strong>, while water vapor applications take place at higher temperatures.<\/p>

When water is heated to its boiling point or higher than that, the water changes its aggregate form from liquid to gaseous. It is then existing as water vapor (steam). If this steam is introduced into any kind of reaction chamber or instrument, it is called water vapor application.<\/p>

In contrast, every gas can transport and contain a certain amount of (liquid) water at any given temperature. This is called humidity. Considering air as an example, there is always an\u00a0amount of water contained in the air, even below the boiling point of water<\/strong>, which is defined as grade of humidity or\u00a0relative humidity.<\/strong><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Humidity measurements<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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The typical temperature range for humidity generator is between room temperature and 80\u00b0C with a controllable relative humidity from 0.2% up to 98%. This can be used for\u00a0applications<\/b><\/a>\u00a0in thermal analytical devices, like\u00a0Dilatometers<\/b><\/a>,\u00a0Differential Scanning Calorimeters<\/b><\/a>\u00a0or\u00a0Simultaneous Thermal Analyzers<\/b><\/a>, especially for the analysis of\u00a0food<\/b>, pharmaceuticals<\/b>,<\/a>\u00a0building materials<\/b><\/a>\u00a0or biological processes.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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That means, the same amount of water, or more precisely, water vapor in the air (grams H2<\/sub>O per kilogram of air) translates into different relative humidity levels, depending on the temperature, as the capacity of the atmosphere changes. This\u00a0maximum amount of water (capacity) is highly temperature dependent and varies from a fraction of grams per cubic meter (at temperatures below 0\u00b0C) to about 600 grams per cubic meter at 100 \u00b0C.<\/strong><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Relative humidity<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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The most commonly used measure of humidity is relative humidity. Relative humidity can be simply defined as\u00a0the amount of water in the air relative to the saturation amount the air can hold at a given temperature multiplied by 100.<\/strong>\u00a0Air with a relative humidity of 50% contains a half of the water vapor it could hold at a particular temperature.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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If the relative humidity is between 0.1% and 100%, the water can exist in the form of water vapor.<\/strong>\u00a0If a relative humidity of 100% is reached and the ambient air is cooled down, the Dew Point (which defines the maximum amount of water, which the air can hold at a specified temperature) is exceeded and the water condenses from the air, in the form of liquid water.<\/p>\n

The residual is an equilibrium between liquid water and water vapor at the specific temperature. On the other side, if the temperature is increased above the boiling point of water (100\u00b0C at sea level conditions), the water in the air can only exist in the form of water vapor.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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In particular, with regard to the living conditions on earth, the indication of the relative humidity is very helpful, since the very narrow range of water vapor concentration in which a mammal, like humans, feels comfortable, can be graphically represented by the indication of the relative humidity.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\n\t\t\t\t\t\t\t\t\tThis leads to two main application cases for thermal analytical applications. The first one is a temperature sweep application where a defined humidity level at room temperature is set and the sample, including environment, will be heated up or cooled down to a preset temperature.\r\n\r\nIn this case, the amount of water inside the measurement chamber stays constant, but the\u00a0relative humidity changes as a function of temperature<\/strong>.\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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The other possibility is to measure under isothermal conditions, which allows to set defined and constant humidity levels between 0.2% and 98% relative humidity. Cold air below room temperature can only hold water vapor in a very limited amount that decreases with temperature. Air below 0\u00b0C can no longer contain water vapor.<\/p>

(see graph above).<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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As soon as the relative humidity is above the dew point (e.g. during cooling down), the water vapor condenses to the form of moisture and, if the surrounding temperature is below 0\u00b0C, it will freeze. This procedure requires more extensive hardware equipment, e.g. a heated transfer line for sample temperatures above room temperature.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Questions? We're just a call away!<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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+1 (609) 223 2070<\/p>

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Our service is available Monday to
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We are here for you<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Applications<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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A humidity generator creates an atmosphere containing water vapor by passing a gas through warm water and saturating it. The gas is then adjusted to a pre-set relative humidity of 100% RH by adding dry air using a dew point sensor. Customized configurations for carrier gas and compositions can be ordered, using additional MFCs or external dew point sensors.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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This application example shows the influence of moisture and humidity on brick material. The left curve shows the isotherms of 2 brick types at 20\u00b0C and 60\u00b0C and the moisture content, the samples adsorbed. On the right side you can see the moisture dependent coefficient of thermal expansion (CTE). The grade of humidity has a significant influence on the thermal expansion behavior.<\/p>\n

P. sin; J. Lukovicova; G. Pavlendova; M. Kubliha; S. Uncik; Experimental Performance of HygroThermal Deformation<\/em>
of Contemporary and Historical Ceramic Bricks, International Journal of Matter<\/em><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Well informed<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Downloads <\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Everything at a glance<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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WATER VAPOR und RELATIVE HUMIDITY Brochure (PDF)<\/b><\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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