How to calculate humidity on a hygrometer: a guide to using the devices + calculation examples

The indoor microclimate plays a big role. Scientists have proven that humidity has a significant impact on human health.Therefore, it is desirable that this indicator always be within the normal range. Do you agree?

Hygrometers are used to measure humidity. They differ in their operating principle and come in different types. Some models automatically detect humidity levels. When using other types of devices, you have to perform a number of actions and make calculations yourself. This requires certain knowledge, so you need to understand how to calculate the humidity on a hygrometer correctly.

Next, we will talk about what types of instruments there are for measuring humidity in a room, and we will understand the principle of their operation. In addition, from our material you will learn how to choose a suitable device for measuring humidity.

What are hygrometers used for?

A hygrometer is a laboratory equipment that is used to measure the relative or absolute humidity of atmospheric air and gases. This device is also called a hygroscope.

Hygrometer is translated from Greek, “ὑγρός” means “liquid”, and “μετρέω” means “measure”. Such a device will be useful both in everyday life and in the industrial sphere.

Humidity, like temperature, is an important indicator of microclimate. It is recommended to support it within the standard: each type of room has its own optimal level. This is good for human health and the safety of things, structures, and food.

Fungus and viruses quickly spread from too humid air, vegetables and fruits begin to rot, and mold on the walls. Condensation, settling on electrical equipment, metal structures, paper, leads to their damage. The chemical composition of drugs is also disrupted.

A dry atmosphere impairs the protective properties of the nasopharyngeal mucosa. This leads to the fact that a person becomes susceptible to the influence of various viruses and infections.

Also, low humidity levels have a bad effect on the quality and safety of food: they begin to wither and lose their beneficial properties. An optimal microclimate is important during construction and repair work, especially if different solutions are used.

There are many types of hygrometers. Their accuracy may vary. The choice of device should be made based on the area in which it is planned to be used

To maintain humidity at the desired level, it is necessary to measure it regularly and take appropriate measures if the indicator deviates from the norm.

The hygrometer is used in various fields:

• Food Industry;
• trade;
• livestock farming;
• crop production;
• pharmaceutical industry;
• greenhouse, municipal services;
• construction, etc.

Despite their usefulness, hygrometers are not widely used in residential areas. They are usually used at weather stations and control services.

It is strongly recommended that humidity levels be measured regularly in hospitals, kindergartens and schools. It is worth purchasing such equipment for your home. By maintaining humidity in a given range, you can significantly improve all areas of your life.

Popular types of devices

The procedure and features of measuring humidity levels with a hygrometer depend on the type of laboratory equipment used. Such devices differ in design, operating principle and a number of other parameters.

By design, hygrometers are either mechanical or electronic. The former have a dial with an arrow, the latter have a display on which information is displayed.

Based on the principle of operation, there are the following types of devices:

• film;
• hair;
• weight;
• capacitive;
• resistive;
• ceramic;
• condensation;
• electrolytic;
• psychometric.

Film hygroscopes have a dial with a pointer. The sensor is a special film. It consists of organic material and is connected to the arrow.

Under the influence of changes in atmospheric humidity, the film changes its size. This causes the hand to move to the right or left, showing the result on the dial.

The advantage of a hair hygrometer is its simple design. This device can be used to determine air humidity at temperatures below zero degrees

The main element of hair devices is fat-free human or synthetic hair stretched over a frame with an arrow. The operating principle of the device is similar to film types of hygrometers.

When humidity changes, hair length changes. This leads to the deviation of the arrow in a certain direction.

Weighing hygroscopes are used to calculate absolute humidity. They are equipped with tubes with hygroscopic material. As the air mass passes through, the filler absorbs moisture and increases in weight.

The sample is taken using a special pump. The system is weighed before and after air injection.Absolute humidity is calculated based on the obtained indicators and the volume of air mass passed through.

Capacitive hygrometers incorporate an oxide capacitor. Its capacity varies depending on the moisture concentration in the air. Such models must be periodically calibrated. This is due to the fact that over time the detector capacity decreases, which affects the accuracy of the measurement.

Resistive hygroscopes work on the principle of changing the level of humidity depending on the electrical resistance of salts and polymers. Ceramic instruments consist of a dial with a pointer. The sensor is a special ceramic mixture (clay, silicon). Its electrolytic resistance depends on the level of humidity.

Ceramic hygrometers only show humidity levels. They have no additional functions. But they are accurate and allow you to monitor changes in the indoor microclimate

Condensation type devices are also called hygrometers Lambrecht. The operating principle of the equipment is based on the use of a built-in mirror. The temperature of this element changes along with the temperature of the atmospheric air.

The main element of electrolytic devices is a glass, polystyrene or other insulating plate coated with a layer of electrolyte. Depending on the moisture concentration in the air, the resistance of the electrolyte changes.

The condensation hygrometer is highly accurate. But it is not suitable for household use due to certain difficulties in use.

Psychometric hygrometers measure the humidity of atmospheric air based on the decrease in temperature of a wetted body. They consist of two thermometers: dry and wet.

The device is also equipped with a feeder - a glass flask that is filled with water.The calculation is carried out by the researcher independently. The table included with the device helps you determine the relative air humidity with a hygrometer.

In addition to instruments, there are alternative ways to measure humidity. More details - read more.

How to use a hygrometer?

Each type and model of hygrometer comes with instructions for use. It should be strictly adhered to. The accuracy of the result depends on this.

Psychometric instruments have two advantages: they are accurate and show not only humidity, but also the temperature level in the room

The data sheet for the device tells you how to correctly measure the humidity level. Provides safety rules and precautions when working with the device. Recommendations are given for the care of laboratory measuring equipment.

Today, in everyday life and at work, as a rule, mechanical, electronic, condensation and psychometric hygrometers are used.

Option No. 1 - electronic devices

Electronic hygrometers are easy to use. They do not require any settings and are completely ready to work. Before use, the device must be inspected for visible defects - cracks, chips.

The algorithm for measuring humidity levels with an electronic hygroscope is as follows:

• turn on the device by pressing the power button;
• if necessary, set the day of the week, time, set an alarm clock and other parameters using the “UP”, “MODE" And "DOWN»;
• wait until the device calculates the humidity level;
• evaluate the result on the electronic scoreboard.

Typically, such hygrometers are used in everyday life. Some people use them in incubators.

Electronic hygrometers have a fairly high level of error.Therefore, you should not completely trust their results; it is better to check the results using a mechanical device

Modern models of electronic hygrometers are equipped with various additional functions: for example, they show air temperature, light level, day of the week, etc.

Option No. 2 - mechanical hygrometers

The accuracy of mechanical hygrometers is low. The error is 5-8%. Before you start using the device, it is recommended to calibrate it. To set up, you need a reference hygrometer that shows accurate humidity values.

You need to place two devices side by side. If the indicator of a mechanical device does not correspond to the reference one, then it must be adjusted using the adjusting screw. This element is located on the rear panel of the equipment.

Mechanical hygrometers can, in addition to the humidity level in the room, additionally show the temperature level. Their accuracy is higher than that of electronic

Using a mechanical hygroscope is quite simple. It is necessary to install the device in the right place (put it on a table or hang it on the wall) and evaluate the result.

Option No. 3 - condensing devices

A condensation hygrometer consists of a thermometer, a metal box and a rubber bulb. It determines the absolute air humidity at the dew point. It is highly accurate. Such a device is usually not used in everyday life.

The condensation hygrometer is quite accurate. But to determine the humidity level you need to perform a number of actions. In terms of ease of use, it is inferior to electronic models

Algorithm for using a condensation type hygrometer:

• pour ether (alcohol) into the box;
• start blowing air with a blower until the first drops of dew appear;
• record the thermometer reading;
• look at the humidity level in the table supplied with the device.

As you can see, there is nothing complicated in determining humidity using a condensation-type hygrometer. Just follow the instructions above.

Option No. 4 - psychometric hygrometer

The psychometric hygrometer is quite accurate. Such equipment is checked by metrological services. The results of this device can be trusted.

Typically, psychometric hygroscopes are used in hospitals, clinics, schools, and public canteens. They also buy them for home use. Psychometric hygrometers are represented by models VIT-1 and VIT-2. You can see what they look like in the figure below.

The VIT-1 psychrometer is used at temperatures from 0 to +24 degrees. VIT-2 is recommended for use in rooms where the temperature ranges from +16 to +40 degrees

Before using the device directly, it is necessary to carry out a number of preparatory work:

1. Unpack the hygroscope. Make sure that the equipment of the device corresponds to the data specified in the passport.
2. Inspect equipment elements for integrity.
3. Remove the feeder from the base. Place it in a container with distilled water, sealed end down.
4. Moisten the wick by dipping the wet bulb bulb into a glass flask filled with water.
5. Install the feeder so that the wick does not touch its walls, and there is a distance of at least 2 cm from the edge of the open end of the flask to the thermometer reservoir.
6. Place the hygroscope in a vertical position at eye level. The psychometric device does not have a stand.The device can be hung on the wall. For this purpose, there is a special hole in the upper part of the product.

After the preparatory stage is completed, you can begin to directly determine the humidity level with a psychometric hygrometer.

The feeder must always be filled with water. The fluid should be added in advance. You need to monitor the water level in the flask. If it is topped up before taking measurements, then you need to wait half an hour, and then start determining the temperatures on wet and dry thermometers

The device should be kept in the measured environment for at least 30 minutes. Otherwise, the accuracy of the result will be questionable.

How to use a psychometric hygroscope:

• stand in front of the device at a distance of good visibility of the scale marks. It is important not to breathe on the thermometers to avoid distorting the results;
• record the readings of a dry-type thermometer. It is located on the left side and has a corresponding mark. Record the result obtained with an accuracy of 0.1 °C;
• take wet bulb readings;
• make amendments to the results obtained in accordance with the recommendations given in the passport for the measuring device;
• subtract the wet bulb value from the dry bulb reading;
• Determine relative humidity using the table located on the right side of the device. The desired value will be located at the intersection of the dry-bulb temperature lines and the difference between the readings of two thermometers.

The figure below shows how humidity is determined using a psychometric hygrometer.

A dry thermometer shows a temperature of 20 °C, and a wet thermometer shows 19 °C. The difference between these values ​​is 20-19=1 °C.In the table, in the column of dry thermometer indicators, we find the indicator “20” and draw a straight horizontal line. In the temperature difference values ​​we find “1” and draw a vertical line. At the intersection of two lines there is an indicator of the relative humidity level - 90%

To psychrometer showed accurate results, you need to regularly carry out its maintenance.

So, the water should be at room temperature. It is acceptable to use boiled liquid. The water must be pre-purified using a filter. It should be boiled for at least 15 minutes.

The reservoir filter of a wet thermometer should always be soft, clean and moist. It is necessary to replace this element periodically. If the air dust content does not exceed 5 mg/cubic meter, then this procedure should be performed every two weeks.

If the parameter in question is higher, then the wick must be changed as it becomes dirty. Before installing a new wick, you need to wipe the thermometer reservoir with a cotton swab dipped in warm water.

The hygrometer should be checked periodically. The accuracy of the device is assessed immediately after release from production. Next, the device should be checked 1-2 times a year.

Rules for safe operation

Although there are different types of hygroscopes, there are general rules that must be followed when using them. All equipment should be handled with care. Do not allow the device to fall.

It is also prohibited to treat the device with aggressive chemicals: for example, solutions containing alkali or acid. It is not recommended to overheat the device.The maximum permissible temperature at which the equipment can be operated is given in its accompanying instructions.

It is important to choose the right location for the hygrometer. There should be no sources of cold or heat near the equipment. The absence of vibration is important. Hygroscopes should not be placed in areas directly exposed to sunlight.

It is important to remember safety precautions when using devices containing toxic substances. For example, the thermometers of the VIT-2 psychometric apparatus are filled with toluene. This is a toxic and flammable liquid.

Therefore, it is important to prevent the device from breaking and overheating. If the tank ruptures, you can remove toluene from surrounding objects with water and detergent.

If you need to use water to measure humidity, then you should use distilled water (even if the instructions do not directly say anything about this). Unpurified tap liquid contains salts that will settle on the elements of the device, reducing its shelf life and the accuracy of the results.

Which hygrometer is better?

Which type of hygrometer is best to purchase in order to control humidity levels depends on the type of room, purpose and frequency of measurements. For warehouses, production workshops, schools and medical institutions it is better to choose psychometer. It has a high level of accuracy and reliability.

For household purposes, a mechanical or electronic hygrometer will be sufficient - these devices can be purchased at your nearest hardware store. In addition, a variety of models will help you choose a device to suit the style of the room.

Psychometric models containing toluene are not recommended for use at home, especially if the family has children and animals. Accidentally breaking a device can lead to a number of unpleasant consequences.

To control the level of humidity in the house, it is better to purchase a mechanical hygroscope. It is more accurate than electronic. At the same time, it lacks many additional functions, unlike the latter type of equipment.

In addition, you can assemble a device for measuring humidity with your own hands. You can read how to do this in this material.

Conclusions and useful video on the topic

The video below describes the principle of operation of the psychometric device and the procedure for calculating the humidity level:

The accuracy of psychometric and electronic hygrometers can be judged from this video:

The most common psychometric devices are VIT-1 and VIT-2. They are accurate and additionally show the air temperature.

Electronic devices can be used for domestic use. They are usually multifunctional and show not only humidity, but also temperature, light, time, day of the week, etc. Their accuracy leaves much to be desired.

Mechanical hygroscopes also have some uncertainty, but they can be adjusted through calibration.

Do you use humidity meters at home? Which device did you prefer and are you satisfied with its performance? Please leave your comments in the block below the article.