Volume-9 (04/2005)

Traceability of surface measurements to national standard platinum rings and plates with a DKD certificate

The measurement of the surface tension by using the ring and plate method can be traced back to a national standard without any difficulty.

An important step is to check the force measuring system used with standards that can be traced back to national standards. This is generally carried out with weights certified by the DKD.
However, it is often forgotten that not only the force represents an important parameter for calculating the surface tension but also the shape of the plate or ring is equally important.

The "Wilhelmy equation" demonstrates this:

---> Bitte Gleichung ergänzen


The force F which acts on the ring or plate is just as important as the wetted length l.


This fact has been taken into consideration by KRÜSS with the result that both rings and plates can now be ordered with a DKD certificate which

• documents that the ring or plate has the correct dimensions
• and uses these to determine the true wetted length.

The firmware and software of the K11 and K100 instruments allows the input of the shape or wetted length. This closes the gap which would otherwise exist for a proper shape certificate for the ring or plate.


If you have any further questions please contact Mr. Hennemann directly.

Dominik Hennemann, Technischer Support, KRÜSS GmbH
Phone: +49 (40) 51 44 01 - 55
Email: service@kruss.de