Product review (5 stars): I'm not sure how precise it is but for its intended use it does and excellent job for a reasonable price
This inexpensive product gives me a reading that matches the settings on my furnace humidifier, which is exactly why I purchased it.  It is located in our master bed room and records an appropriate increase when I take a shower.  I'm not sure how precise it is but for its intended use it does and excellent job for a reasonable price.