Hygrometer

The following text is designed to assist you in purchasing a hygrometer. However, should you have any questions about the hygrometer products found on this website, please do not hesitate to contact the PCE technical support team at  or +44 (0) 2380 987 035 for PCE Instruments UK, or at  or +1 (561) 320-9162 for PCE Americas Inc.

Accuracy is a key component to consider when buying a hygrometer. When looking at different hygrometer devices, it is important to evaluate the hygrometers based on the level of accuracy required for your application, as a high-accuracy hygrometer product typically comes with a higher price tag. For example, a high-accuracy hygrometer would be essential for a food safety inspector, as stringent standards must be met when it comes to food storage and refrigeration. In contrast, if you are in search of a hygrometer for use in your home, a device with lower accuracy would provide you with an adequate estimate of the relative humidity indoors.

For temporary humidity measuring applications (such as simple control measurements, spot checks to assess concrete drying conditions, or evaluations of heating, ventilation and air conditioning (HVAC) system performance), a portable handheld hygrometer without memory may be used. Portable hygrometer devices often are ergonomically designed to allow for quick, easy and comfortable one-handed operation.

For long-term or continuous monitoring of relative humidity, a fixed hygrometer with memory and data-logging capabilities is ideal. Many fixed hygrometers with memory record and store date- and time-stamped humidity measurement data either to an internal memory or a removable SD memory card. Depending on the model, some hygrometers for continuous monitoring also record and store peak values (minimum and maximum) and/or emit an alarm when a certain user-defined threshold of air humidity is reached. Most data-logging hygrometers allow the stored data to be transferred to computer using special software, a USB or RS-232 interface cable and/or an SD memory card reader. Data transfer to a computer makes documentation and reporting easy, as measurements do not have to be written down by hand. In addition, some hygrometer products save the data in a Microsoft Excel-compatible format.

Stationary hygrometers used for the continuous monitoring of climate-controlled environments like refrigerated trucks, storage units, warehouses and museum archives are used to survey indoor environmental conditions in the context of safety and quality assurance. Hygrometers with memory also aid in documenting an organization's compliance with industry standards and best practices. Hygrometers for permanent installation usually come with the necessary brackets or hardware required for mounting the device on a wall or DIN rail. Often a fixed-installation hygrometer instrument is equipped with a kickstand or tripod, so the device can be positioned as needed on a desk, table, counter or workbench. If it is necessary to read the humidity measuring results from a distance, a hygrometer with a large and easy-to-read liquid crystal display (LCD) should be selected. In addition, when working in low-light or dark environments, it is critical that the display be backlit.

Again, application plays an important role when selecting a hygrometer. For non-professional use, a simple hygrometer that only needs to be switched on to start measuring is recommended. Most professional usages will require a hygrometer with more advanced functions. Bear in mind, the more functions a hygrometer possesses, the more complex the hygrometer will be to use. However, experienced contractors, technicians and engineers will be more than comfortable using a hygrometer with added functionality, as digital hygrometer menu structures are somewhat standardized throughout the test, measurement and inspection equipment industry. If a hygrometer has many different functions, it can be helpful to have several buttons or keys on the device, as more keys can provide time-saving shortcuts for navigating a device's menu structure. In just-in-time (JIT) manufacturing environments, even the smallest time savings can be a tremendous asset. Another point to consider regarding keys is their size. For example, in the food processing industry, bigger keys are desired to accommodate users required to wear protective gloves.

The hygrometer's material and ingress protection (IP) rating are additional factors to explore before buying. Depending on the anticipated operating conditions, your hygrometer may need to be made of a durable material such as high-quality ABS plastic. Your hygrometer's housing also may need to be dustproof or waterproof. The IP rating system is a widely recognized set of international standards related to an electronic device's ability to protect against the intrusion of foreign bodies. This rating is typically presented as the letters I and P followed by a two-digit number, i.e., "IP##." The first digit of the number pertains to solids (dust), while the second digit pertains to liquids (water). The higher the digit, the greater the level of protection afforded by the device.

Lastly, don't forget to evaluate the hygrometer's power supply and accessories. If your hygrometer is powered by batteries, the batteries should be a commonly used size so they are easy to find and affordable to replace. If your hygrometer is powered by an AC adapter, take care to ensure the power cable won't interfere with other aspects of your work environment. Many PCE-brand hygrometers offer replacement parts like spare batteries, sensors, cables and adaptors as optional accessories. In addition, an ISO calibration certificate can be obtained as an accessory for most PCE-brand hygrometer products.

The term hygrometer comes from the Greek words hygro (meaning “wet, moist; moisture”) and metron (meaning “a measure”). Thus, a hygrometer is a device used to measure moisture in the air, i.e., humidity. In modern measuring technology, a hygrometer often is used in combination with a temperature measuring instrument. The measured values for relative humidity and temperature can be used to in tandem to measure dew point or water vapor content. Frequently, a hygrometer also is mistakenly referred to as a hydrometer. However, these two types of testing devices do not have much in common. In contrast to the hygrometer, which measures humidity, a hydrometer measures the density or a specific weight of a liquid.

Humidity, also called relative humidity or air humidity, is defined as the amount of water vapor in the air. However, humidity is relative. It is normal and even important that air contains water vapor. The amount of water vapor in the air depends on several factors, including the temperature of the air. Warm air is generally more humid than cold air. This means that when air temperature decreases, the maximum amount of water the air can hold also decreases. A hygrometer displays readings in a percentage of relative humidity (% RH). So, if a hygrometer displays a measuring result of 20% RH, then the air holds 20% of the maximum amount of water possible at that temperature.

When the air is humid outdoors, water and sweat evaporate more slowly. Fog, dew and precipitation become more likely. Indoors, high humidity can trigger symptoms for those suffering from allergies, asthma and chronic obstructive pulmonary disease (COPD). Excessive condensation also can form in overly humid indoor environments, resulting in the growth of mold and bacteria. However, when the indoor air is too dry, skin becomes itchy and dry and can even crack. Some people also experience problems with nose bleeds in very dry climates.

When the air is too humid indoors, it can sometimes be enough to simply open some windows and doors. Other times, the performance of the HVAC system should be evaluated by a trained professional. In extreme cases, a more complex measure must be taken, like the installation of an extractor fan. In many instances, a reliable hygrometer can be used to identify the root of the problem.