There are two groups of paper moisture meters: Absolute paper moisture meters and Relative paper moisture meters. Both groups show humidity results in % however their range of application is different. Absolute paper moisture meters are mainly used by the manufacturer directly in rolls of paper-making machines (these are not mobile so they never take measurements from roll papers when they are moving) or by the printer during the input control in the printing office. The control of humidity in paper is specially important during its productive process due to the fact that an excess of moisture may block the rotary machine and warming the paper rolls.