The actual working ranges of industrial equipment are increasing constantly. This applies also to web and coil processing equipment being capable of handling very thin and narrow webs but also heavier and broader webs. This results in extremely high requirements regarding the accuracy of web tension measurement and control.
HAEHNE has selected an easy approach to achieve high resolution and accuracy resulting in a substantially lower cost solution. Typically web tension sensors have an overall measurement error of 1.0 or 0.5 %. If such a sensor is used in lower measuring range, the total error becomes unacceptably large and not suitable for measurement and closed loop control. For this purpose web tension sensors with an overall measuring error of 0.1 % have been designed which improve the measurement results by a factor of 5. This means that now it is possible to measure and control the forces in the lower range precisely. Important is also, that such a sensor is not only protected in the large force range by mechanical stops (tenfold overload of nominal range) but also in the lower force range by the intrinsic nature of the design.
The accuracy for small forces can still improve in this very precise measurement by spreading the measurement range. Therefore a corrected nominal value is determined in the lower force range.
The calibrations are stored in the associated HAEHNE amplifiers DCM or DCX.
For example by switching the measuring range at 10 % of nominal force the accuracy of 0.1 % refers to the 10 % of the nominal forces.
Successful installations are a proof that this approach is not only cost-effective but also very a robust under both mechanical and electrical considerations.