For human life, humidity affects health a lot. If the humidity is too high 90%, world will boost the hazard of arthritis, cough, asthma, headaches and several various other chronic diseases. Irritating fatigue, as well high humidity is also a problem for harmful bacteria and fungi come grow. Also affects electronics and also furniture in the house. Have you ever wondered what humidity is the can impact your life so much. How have the right to we measure moisture and also how perform we boost or diminish it? This article will help you answer this questions.

You are watching: Relative humidity can be measured with a

1. Humidity

Humidity is the concentration of water vapor presenting in the air. The steam, the gas state the water, is difficult to see with the person eye. Humidity shows the opportunity of rain, mist, or fog. The higher the humidity, the less reliable it is to cool under our bodies, i m sorry is why sometimes hot summers don’t make us as uncomfortable as warm humid loss days.

Fog in a tropic rainforest (Source: Wikipedia)

Humidity has 3 concepts: absolute humidity, family member humidity and specific humidity.

Absolute humidity defines the water content of gas and also is express in grams per cubic meter (g/cm³). However, pure humidity changes when the air push changes. This is extremely inconvenient for technical chemistry calculations (e.g because that a apparel dryer, due to the fact that its temperature have the right to vary significantly). Thus absolute humidity is often identified in design chemistry as the mass of water vapor every unit massive of dried air.

Relative humidity shows the existing state of absolute humidity family member to preferably humidity in ~ the exact same temperature, expressed as a percentage (%).

Specific humidity is the ratio of the mass of water vapor come the full mass that the humid air.

2. Loved one Humidity

The loved one humidity (RH or ϕ) of the water-gas mixture is identified as the ratio between the partial push of the heavy steam

and also the saturation vapor press of the water
at the exact same temperature, expressed together a percentage:


Relative humidity is usually expressed together a percent (%); The much more humid the air, the higher the relative humidity. As soon as the loved one humidity get 100%, the waiting is already saturated v water vapor and also is in ~ the dew point(1).

Relative humidity is different from absolute humidity – identified as the fixed of water vapor contained in 1 m³ that air. Absolute humidity walk not suggest the humidity level that the air due to the fact that at a lower temperature the much more water vapor in the wait is saturated. Therefore, to explain the humidity the air, loved one humidity is used. Relative humidity have the right to be measured through a hygrometer, dubbed a hygrometer.

(1)The dew allude is the dew condensation suggest of an waiting mass, in ~ a consistent atmospheric pressure, the temperature at which the water vapor content of the air mass condenses into liquid water. In various other words, the dew suggest is the temperature in ~ which the relative humidity that the air mass reaches 100%.


Dew condenses on the leaf

3. The Difference in between Humidity and Relative Humidity

Humidity is the quantity of water vapor in the atmosphere, and also relative humidity is a concept of humidity.

Humidity is the water contents of the mixture of heavy steam and other elements present in the air. Family member humidity is the percentage of water vapor in the air in ~ a provided temperature.

Humidity is supplied to identify the likelihood that rain, fog or mist occurring.

Relative humidity is supplied for climate control and how the affects human’s health, comfort and also safety. 

Relative humidity is likewise used come ensure safety and security for machines, vehicles and also buildings. Additionally determining the humidity the a certain place provides data to projection the weather.

4. Technique of measure up the loved one Humidity

Currently, there are 3 key methods offered to measure humidity: electronic hygrometer, psychrometer and dew point measuring device. The dew suggest measuring an equipment is the many accurate and also is frequently used as a traditional for calibrates.

Electronic hygrometer based upon sensors such together capacitance, resistance, gravity, and optical to measure humidity, accompanied by a temperature sensor to measure up the ambient temperature. 

Principle of loved one humidity measurement for capacitive hygrometer, air flowing in between two metal plates, the readjust of wait humidity is proportional to the capacitance adjust between the two plates. 

For a resistive hygrometer, the polymer or ceramic absorbs moisture, which then affects the resistivity and also is connected to an electrical circuit in i m sorry the moisture affects the resistance that the material. From over there the loved one humidity is determined based on the readjust in the current. This measurement an approach is suitable for measure up humidity between 15% and 95%, v an apprehension of ± 3%.

In fact, to measure the family member humidity, capacitance type sensors are often used, since capacitive sensors room cheaper and much more reliable than other sensors. However, the to trust of the sensor depends greatly on the operation environment. If working in an environment with a many dust or solvent gases, the sensor will damage much more quickly, for this reason there have to be a dust filter to expand the life of the sensor.

Types of digital hygrometer (Source: ThermoPro)

The Psychrometer has actually two thermometers, one wet bulb and also one dry bulb thermometer. The bulb of the wet pear thermometer is covered with a wet cloth. Once the psychrometer is “suspended” or rotated, waiting is blown v both thermometers. The wet bulb thermometer is cooled by evaporation, and its reading decreases. The loved one humidity is determined by compare the wet and also dry thermometer pear temperatures. The lowest possible measurement hesitation is ± 4%.


Psychrometer (Source:

The dew allude measuring device is structured as presented in picture. The sample is inserted into a jar through an electrically cooled winter face. The mirror surface is cooled till the light resource detection device detects dew development on the mirror, and also the condensing temperature is measured with a sensor attached to the mirror surface. The dew suggest is the temperature at which the sample becomes saturated v water. Therefore, this temperature is pertained to the humidity level in the sample. A microscope is also noted in the instrument so the the thickness and nature of the condensate have the right to be observed. Even small levels of contaminants on the surface of the mirror deserve to cause huge variations in dew point, and also therefore the instrument have to be kept very clean. When necessary, the mirror have to be cleaned v deionized or distilled water.

Construction of a dew point measuring an equipment (Source: book Measurement and also Instrumentation, 2nd Edition Theory and Application by Alan S Morris, Reza Langari)

5. Necessary of Measuring and Monitoring of relative Humidity

By far the best reason to monitor relative humidity is to control the humidity around the finish product. In most cases, this method making sure the RH never ever gets also high. For example, let’s take a product prefer chocolate. If the RH in the warehouse facility rises over a particular level and also remains over that level because that a sufficiently lengthy time, a phenomenon recognized as blooming may occur. This is wherein moisture develops on the surface of the chocolate, dissolve the sugar. As moisture evaporates, sugars kind larger crystals, which leader to discoloration. 

Humidity is likewise a big problem for commodities that are exceptionally sensitive to moisture, together as part pharmaceuticals. This is since it can change the nature of a medicine product till it becomes useless, which is why products such as clinical pills and dry powders are stored under controlled conditions (control at an exact humidity and temperature).

Humidity and also temperature monitoring for vaccine, pharmaceutical warehouse

Finally, family member humidity is also a crucial factor in building automation equipment – emphasis on human comfort, such together air conditioning. The capacity to measure and control RH not only helps to preserve a comfortable atmosphere inside the building, but also helps optimize the efficiency of the HVAC system(1) by offering an clues of the quantity of external air. The intake have to be conditioned, based upon the external temperature.

(1)The abbreviation the Heating, Ventilating, and Airconditioning is collectively referred to as the air air conditioning system.

6. Humidity measurement Device

Humidity measurement machine (moisture analyzer) is a familiar and popular machine in everyday life. Friend can conveniently see the screen of temperature and also humidity in ~ airports, restaurants, many hotels … that is also a kind of humidity measure up device.

Humidity measurement device is a an equipment made and also manufactured to offer the duty of determining the humidity (the ratio of water) in the environment, waiting or a particular substance. For instance in the species of materials: wood, paper…; types of building materials: mortar, concrete, wall…; fiber materials: cotton, fabric…; medicines and also pharmaceuticals in health; preserving agricultural products, foodstuffs.

Humidity measurement maker is really diverse. Since old times, world have produced tools such together hair hygrometer, wet dried moisture meter, dew point hygrometer … to measure humidity and also apply to measuring humidity in the air, some agricultural products … The tools room rudimentary, manual and also the accuracy is no high. Nowadays, with the advance of science and technology, we have an extremely convenient and useful electronic humidity measurement devices.

Classic hygrometer (Source:

Currently, humidity electronic measurement gadgets are more commonly used because of the quick and convenient lock provide. These tools are modernly designed, apply progressed and intelligent technologies not only measure the surface moisture of products but additionally have the capacity to measure moisture inside, through countless layers that materials; aid users save a many time, effort and attain high efficiency.


Some popular species of hygrometer (Source: maydochuyendung)

According come this classification, the hygrometer is separated into 7 main groups:

Moisture meter for wood, paper, sawdust, wall, concrete. This group consists of the varieties of: timber moisture meter, concrete wall surface moisture meter, soil moisture meter … castle are largely used in the areas of woodworking and processing, construction, farming …Moisture meter because that grains and agricultural products. This group contains moisture meters because that grains, grains: rice, coffee, flour, etc. And mainly applied in agriculture and food and also food handling production.Moisture meter for cotton, fabric, fiber. This group is greatly used in the garment industry. They assist users determine the moisture content of fabrics.Moisture meter because that coal, commercial chemicals. This group is qualified of measure up the moisture contents of a wide range of materials in the chemistry industry.Humidity meter, air temperature. This team is mostly used because that the activities of security temperature and humidity, research tasks and analysis of weather and also climate. In addition, this group additionally includes hygrometer, portable thermometer – devices generally used in homes, warehouses, restaurants, many hotels …Moisture analytical balance (moisture evaluation balance), this model deserve to be a really versatile an equipment that can have moisture analysis scale models that carry out the features of all 6 above machines. Lock are typically used in measurement laboratories for research study purposes.7. Humidity linked Temperature Controller

With the prominence of measuring and monitoring humidity outlined in ar 5 and also the hygrometer introduced in ar 6, we deserve to see the measuring and also monitoring humidity and temperature is very necessary for countless fields and also trades in human being life. So have actually you ever wondered, after ~ measuring the humidity and also temperature parameters v a handheld machine or sensor, just how do we want to boost or decrease the humidity of one environment. This ar will help to answer her question around relative humidity and also temperature controllers.

Humidity and temperature regulate can it is in via an integrated set of sensors and controllers. This is the most basic control method but the error will be high. To control for much more advanced systems, we require humidity sensors through an calculation of 4-20mA current, voltage 0-10VDC. That can connect with a PID controller or PLC for an accurate humidity and also temperature control, data collection and also remote monitoring.

Controlling humidity and temperature, the an initial thing is the we require a humidity sensor with integrated temperature measurement. The most vital factor in the humidity manage process. Need to be a sensor with high reliability, stable operation, quick response. Below we have the right to refer to humidity sensors incorporated temperature measurement functions of part brands such as: Omron, PCE,, …

Integrated wireless humidity sensor by

Secondly The most vital is the humidity and temperature controller, in the controller over there is PID regulate mode with analog calculation 4-20mA, 0-10VDC. As soon as the controller has integrated PID mode, the controller will immediately maintain the desired humidity and also temperature without having actually to collection many complicated parameters. As lengthy as the user selects the preferred humidity and temperature, every little thing for the controller come work.

See more: Solved Farsightedness Can Usually Be Corrected With A, Vision Correction

System control and monitoring temperature, humidity

In addition, humidity and temperature controller, we can pick to incorporate RS485 communication port. With this port we can affix the humidity and temperature controller to the computer or laptop. We can observe and also control humidity indigenous a street without having actually to walk to the controller area. Moreover, collecting data and storing details according to the sampling bike is no much longer a an overwhelming problem. Through the connection to a computer, we have the right to store all the humidity and also temperature data over time.

Normally, the humidity and also temperature controller will manage the calculation which room mist generators, warm fans, waiting conditioners, convection fans, …

8. Conclusion

The quantity of knowledge about relative humidity is so lot that we cannot explain it every through just one article. However we hope the the short article can aid you partially understand more about loved one humidity, the prominence of measuring and monitoring family member humidity in life roughly us and also ultimately help you come understand much more about the function and exactly how each component works in a finish humidity regulate system. If you are interested in more details or have questions regarded the article, please contact us in ~ info