Patent ID: 7895907

Claim:
Method for measuring the tensile stress of a running web ( 2 ) using at least one sensor ( 10 ) which has at least one Wheatstone bridge ( 11 ) containing at least one force sensor ( 7 ) which is influenced by the tensile stress of the running web ( 2 ), a diagonal voltage ( 17 ) of the at least one Wheatstone bridge ( 11 ) being amplified by an amplifier ( 18 ) which outputs a tensile stress signal (Z 0 ), characterized in that the at least one Wheatstone bridge ( 11 ) is periodically loaded by at least one resistor ( 26 ) using at least one intermittently driven switch ( 24 , 25 ) during loading by the tensile stress of the running web ( 2 ), the functionality of the at least one sensor ( 10 ) being determined from the extent to which the tensile stress signal (Z 1 ) is influenced by the loading and being output in the form of an error signal ( 28 ).