If you need to install humidity monitors, the most obvious choice is to buy one of the more advanced data loggers, as they are much more useful than simple hygrometers. There is a wide selection of humidity monitors available and you will have to choose those that are suited for your needs. Many humidity monitors require a computer to view the humidity data that they collect. There are some stand alone modules, however, (ThermaViewer is one of the examples).

Before you decide to buy your data loggers, make sure you have considered all the important factors.

Monitoring range and accuracy

All temperature and humidity monitors have their specific maximum ranges. Be sure to select one that will measure the proper range for your application. Some date loggers will only measure humidity between 20% and 80%. If you need to monitor and document humidity that can go as high as 98% insure that the sensors will respond to that range. Also the accuracy and sensor rate is important to consider. Data loggers with too low accuracy and sample rate will be useless, but if they have them much higher than you need, you'll pay for things you won't really use.

Size

Choose your humidity monitors' size carefully, especially if there is little room to install it. Remember that there are different data loggers needed for freezer trucks than for medicine freezers.

Installation

The last, but not least, check how the humidity data loggers are installed. While most of them (like ThermaViewer) are pretty easy to install, there are some that will need a specialist to properly setup.

Generally, make sure that you know exactly what you are going to buy before you buy it.