Soil Master destroying roots?

I bought one of the Soil Master pH, moisture, and light testers, but it has two pencil size prongs that you puch into the soil, and roots.
http://www.mosserlee.com/SiteContent/Documents/Image/most1.jpg

Is it destroying the roots every time I put it in a the soil, it says dont leave it in the soil for "pronlonged times" so I cant just leave it in there?

bump^^^^^^^