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AquaFlux Questions >  Answer 7

AquaFlux Answer 7

AquaFlux calibration - why, how often, by whom & how ?

Why ?

    Calibration is crucial. Use multiple instruments, share data with collaborators, relate what you did yesterday with what you plan for tomorrow, defend your claims in court - the list is endless. The alternative is normalisation, but that wastes information.

How Often ?

    You should check the flux density calibration at 3-6 month intervals, or before a major study. You can do this yourself in about half an hour using the calibration accessories supplied with the instrument.

By Whom ?

    By you of course! You can also get it done as part of a Passport Service, but that involves cost, shipping and delay. Calibration accessories (calibrated micro-syringe & calibration caps) are supplied as standard with the instrument, so what's to stop you? The software handles all the calculations and you're done in less than half an hour. At the end you have the choice to use the new calibration or to discard it, so nothing is lost if you don't quite get it right.

How ?

    The AquaFlux uses the Droplet Method of calibration [1, 2], which has been verified by an independent Standards Laboratory (National Physical Laboratory, UK). Not only can this calibration be traced to fundamental measures, it has also been shown to bring condenser-chamber AquaFlux and open-chamber Tewameter readings into closer agreement.
Calibration by the droplet method ensures that you get consistent measurements from instrument to instrument and from time to time. There is an additional calibration that cannot be performed by users because it needs specialised equipment. This is the calibration of the sensors in the measurement head. This calibration does not affect the flux density readings directly, but it is nevertheless important. We recommend that you have this done annually, as part of a Passport Service.


[1]   RE Imhof & the TEWL Calibration Consortium. Towards a Traceable Calibration for Trans-Epidermal Water Loss. Post-deadline Poster, Stratum Corneum IV Congress, Paris, June 2004. Click here to download in pdf format.

[2]   P Xiao, RE Imhof, MEP de Jesus, Y Cui & the TEWL Calibration Consortium. A New Calibration Method for TEWL with Traceability to Measurement Standards. Contributed Talk, US-Regional ISBS Meeting, Orlando, October 2004. Click here to download in pdf format.

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