DKFA Magnet Holder with StrainPad

Surface strain measured without glue: two springs and two knurled screws press the StrainPad – an encapsulated foil strain gauge of 10 mm diameter and 0.2 mm height – so firmly against a ferromagnetic surface that friction takes over the task of the adhesive.

What the gauge then reads is the surface strain, in the same quality as a bonded gauge, and it reads it within seconds instead of the three quarters of an hour a bonded gauge needs to be prepared, glued and cured. The holder is taken off as quickly as it went on and used again on the next measuring point; nothing is drilled, nothing is ground, nothing is consumed. It cannot be overloaded – instead of damage an offset appears.

Measurement

• Direct reading of the surface strain, like a bonded strain gauge
• Maximum strain ± 800 µm/m
• 350 Ω foil gauge, k = 2.0 ± 3 %
• Uniaxial, 0.6 mm constantan grid, polyimide encapsulation, Ø 10 mm at 0.2 mm height
• Accuracy < ± 0.5 % of full scale, transverse sensitivity −0.1 %
• Cannot be overloaded – an offset appears instead of damage
• 1,000,000 load cycles at 300 µm/m strain
• Passive – no amplifier inside; recommended bridge voltage 1 V, 10 V at most

Mounting and use

• Holds magnetically – no drilling, grinding or gluing
• Mounted and removed in seconds, reusable
• Contact force 100 … 300 N, settling time 15 minutes
• Smallest radius of curvature 3 mm
• Operating temperature 5 … 60 °C, reference temperature 23 °C
• Temperature matching of 10.8·10⁻⁶ 1/K for ferritic steel is possible
• Holders made of aluminium
• For dynamic applications, for checking FEM calculations and for stress analysis

Versions

Shown is the magnet holder with StrainPad. Other standard holders are available and individual ones are built to the application. Tell us the measuring point and we will name the holder that fits.