A bit of help here from Tkach Enerteprises - makers of the Fermometer.
Product information can be found at:
Products
The product is water resistant, not water proof. Don not submerge for extended time periods (hours). Do not leave in direct sun for extended time periods.
The...
Correction to all from Tkach Enterprises, distributors of the Fermometer.
See this url for instructions and information on accuracy:
http://tkachenterprises.com/Products.html
They are highly accurate and they are not made in China. Multiple crystals being "lit" reflect the variations...