How to buy a humidity monitor

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.