Calibration procedure:

For the calibration of shear sensors, a special shear probe calibration system is used (left). The probe rotates about its axis of symmetry at 1Hz under an angle of attack in a water jet of a constant velocity. At different angles of attack the rms. voltage output of the probe is measured.



The probe sensitivity is the slope of the regression (best fit of a cubic approximation) obtained from the equation:  E/(qU2) = S·sin2α

E is the rms. voltage output of the probe
q is the density of water
U is the velocity of the water jet 
α is the angle of attack
S is the shear sensor sensitivity in (Vms2)/kg.

Intercomparison with shear probe calibration systems in U.S.A. and Canada have shown 
the accuracy and reliability of the ISW shear probe calibration system.

The customer gets a calibration sheet containing the following information:
•   Shear sensor sensitivity (in Vms2)/kg 
•   Measured shear sensor rms. voltage output at various angles of attack
•   Graph og regression as described above