Most people are familiar with relative humidity as discussed by the local weather reporter. Humidity has a significant effect on comfort as most of us know. Very few people realize that humidity is important to scientists and engineers in many different ways. Weather reporters, scientists and engineers all need some way to measure humidity. This short article will describe some types of humidity sensors commonly used to get the measurements.

Humidity is the measure of water vapor suspended is air or other gas. Water vapor is invisible when suspended in a gas. Fog, steam, rain, clouds or other precipitation are water condensing out of suspension and becoming visible (and wet). Scientists have different methods to measure humidity in terms directly related to the way the measurements are used. Some humidity measurements can be mathematically converted to other measurement scales (within certain limits).

The most often used humidity scales are absolute humidity, relative humidity and dew point. These types of measurements, although measuring the same thing, have different units of measure. The way the measurements are used determines the best method and scale for a particular application.

Most people have experienced the “bad hair day” that is caused by high relative humidity. Scientists used the changes in human hair to detect and indicate relative humidity in early sensors. Horse hair was also used in mechanical devices to indicate humidity. When material science began producing artificial materials such as nylon, researchers soon realized these synthetic materials were more predictable and more accurately calibrated. The evolution of humidity measurement has led to the solid-state humidity sensor that is relatively cheap, extremely accurate and damage resistant.

The temperature at which water vapor begins to condense out of a gas at a specified pressure is called the dew point. It is a common weather report term. It is also important in scientific calculations and is used in manufacturing situations or processes. The first dew point instruments used a chilled mirror to determine the temperature of condensation. These sensors were expensive and difficult to keep calibrated. Electronic technology used in modern dew point sensors can make measurements at temperatures as cold as -40degrees F.

The third common humidity measurement is absolute humidity. This is the calculation or measurement of the weight (actually mass) of water vapor in a volume of gas. This measurement is expressed as grains per cubic foot or grams per cubic meter. Absolute humidity is the most useful measurement for calculations and is found in many applications. Electronic sensors can measure absolute humidity in gases as hot as 200 degrees C., even in polluted environments.

Engineers sometimes encounter problems with manufacturing processes that are related to humidity. With modern sensors the environment can be monitored and the process adjusted for better results. Painting processes are particularly sensitive to humidity changes.

The demand for humidity sensors has prodded the development of a wide range of sensors from several manufacturers. Engineers can choose combinations of cost, robustness, measurement range and accuracy to meet any sensing requirement. The internet is the best starting point for sensor research. The researcher can quickly see the range of available products and which best meet the requirements.

Author Bio: Our qualified technicians have over 30 years of experience in providing instrument calibration services and full service repair. We provide a wide range innovative technical solutions, including data loggers, humidity sensor, and pressure transducer.

Category: Home Management
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