How to Choose a Digital Hygrometer

Assess Needs

• 1

  Decide if the digital hygrometer will be for indoor or outdoor use. Outdoor hygrometers are waterproof, rugged and designed for extreme swings in humidity. Indoor hygrometers are often (but not always) designed for greater accuracy.

• 2

  Decide what level of accuracy is required. The accuracy of hygrometers varies by model and price, and margin of error varies from 1 to 5 percent. For most applications a high degree of accuracy is not needed, but monitoring of highly sensitive objects (such as many museum artifacts) will require great accuracy. To improve accuracy, use a psychrometer to calibrate hygrometers.

• 3

  Decide if the hygrometer will be for spot-checking conditions or constant monitoring. Hygrometers used for spot-checking are very different than models designed for constant monitoring. Dataloggers are special types of digital hygrometers that record constant data (at user-specified intervals), which can be downloaded into a computer. 

Choosing a Digital Hygrometer

• 4

  Choose a stand-alone digital hygrometer if constant monitoring is not needed. Standard models also provide temperature information and the maximum and minimum readings over the last 24 hours. Accuracy depends on price, and if accuracy is not necessary (5 percent margin of error), this type of digital hygrometer is inexpensive.

• 5

  Choose a model with a sensor. If the read-out of the hygrometer will be in a separate space from where measurements will be taken, you need a sensor. The sensor can be attached with a cable or wireless (cables are usually more accurate). This type of digital hygrometer is useful when the sensor will be outside or in an exhibit case, but the user wants to record the measurements in an area with easier access.

• 6

  Choose a portable, digital psychrometer if you need mobility and quick readings. For some applications, a user will need to move the digital hygrometer from location to location. A handheld, digital psychrometer with built-in sensor is useful for mobility. This instrument will adjust more rapidly to changing environments when moved to provide faster readings.

• 7

  Choose a datalogger when constant monitoring is necessary. Dataloggers record constant data in user-adjusted intervals that can range from seconds to hours. This is critical in certain situations (such as in humidors or museum exhibit areas) when it is necessary to provide a constant, unchanging (or little changing) humidity level for preservation purposes. Data can be downloaded into a computer to view graphs and tables and alert users to humidity problems.