The C+K probes and devices are high precision measurement tools. We recommend sending the systems to the manufacturer or an authorized agent every two years for a complete calibration. You will get a calibration certificate, which is important for your internal documentation.Literature:
Practical Aspects of Cosmetic Testing - How to 
Set up a Scientific Study in Skin Physiology
Fluhr, Joachim W. (Ed.) 2nd Edition., 2020, 317 p., Hardcover ISBN: 978-3-030-44966-7
eBook ISBN: 978-3-030-44967-4
This book is indispensable for all scientific skin testing in the laboratories of the cosmetic industry. In it you will find all our experiences working in the field of skin testing devices for almost 35 years. It offers a wide range of elementary knowledge and practical advice on how to perform efficacy tests. All authors are recognized experts in their field. It is available in the Springer publishing house and directly from C+K for a special price, just
Interesting information, guidelines, regulations and laws regarding tests of cosmetic products
The European Expert Group of Efficacy Measurement of Cosmetics and Other Topical Applied Products EEMCO
http://www.eemco.net
The European Cosmetic Care Association: Cosmetics Europe (previously COLIPA) www.cosmeticseurope.eu
Interesting courses and education programs:
Online Master course in Cosmetic Science of the University of Cincinnati by Prof. Randolf Wickett and others: http://pharmacy.uc.edu/program-information/graduate/cosmetic/faculty
Intensive Course in Dermato-Cosmetic Science and/or safety Assessment of Cosmetic Products by Prof. Vera Rogiers at the Free University of Brussels: www.dermatocosmeticcourse.eu and http://www.safetycourse.eu
University of the Arts London -London College of Fashion: MSc in Cosmetic Science: www.fashion.arts.ac.uk/courses/integrated-masters/msc-cosmetic-science
Università degli studi die Pavia - Dipartimento di Scienze del Farmaco http://www.unipv.eu/site/home/didattica/post-laurea.html
Australia's first Diplomas in Personal Care and Cosmetic Science: www.personalcarescience.com.au
This is only a small selection of claims and methods to use in this context:
HYDRATING, MOISTURIZING, NOURISHING, BALANCING, NORMALIZING, VITALISING: Corneometer®, Corneofix®, Visioscan®, Sebumeter®, Sebufix®, Tewameter®, MoistureMap, Drop Angle Meter
AGAINST OILY SKIN/HAIR/SCALP, OIL RESTORING, AGAINST DANDRUFF: Sebumeter®, DandruffMeter, Meibometer®
pH-NEUTRAL, RESTORING, REPAIRING, PROTECTIVE, SOOTHING, BARRIER ENHANCING, ANTI-ALLERGIC, ANTI-IRRITANT, ANTI-POLLUTION, ANTI-DRY EYE: Tewameter®, Skin-Colorimeter, Skin-pH-Meter, Corneometer®, Skin-Thermometer, Visioscan®, Mexameter®, Corneofix®, Sebumeter®, Sebufix®, Meibometer®
CLEANING, PURIFYING, ANTI-BACTERIAL, ANTI-ACNE, ANTI-IMPERFECTIONS, PORE ACTIVITY REDUCING, PORE REFINING: Sebumeter®, Skin-pH-Meter, Visiopor®, Sebufix®,
SUNSCREEN, WHITENING, ANTI-DARK SPOTS, ANTI-AGE SPOTS, ANTI-DARK CIRCLES, ANTI-COUPEROSIS: Mexameter®, Skin-Colorimeter
COLOURING, COLOUR PROTECTION, CONCEALING, SKIN TONE CORRECTING, SELF TANNING/TANNING ENHANCING: Skin-Colorimeter
SHINE ENHANCING/DECREASING, GLOSSYNESS, LUMINESCENCE, RADIANCE, BRIGHTNESS, MATTIFYING: Skin-Glossymeter, Skin-Colorimeter
TONING, FIRMING, AGAINST SKIN FATIGUE/SLACKNESS, ANTI-CELLULITE/STRECH MARKS: Cutometer®, Visioscan®, CutiScan
ANTI-WRINKLE, FILLER EFFECT, RESTRUCTURING, REMODELLING, REJUVENATION, ANTI-AGE, STRUCTURE IMPOVING, SMOOTHNESS: Cutometer®, Visioline®, Visioscan®, CutiScan, MoistureMap, Frictiometer
SKIN RENEWAL, EXFOLIATION, AGAINST DRY/SCALY SKIN: Corneometer®, Corneofix®, Tewameter®
MICRO CIRCULATION ENHANCING, WARMING/COOLING, THERMAL PROTECTION: Skin-Thermometer, Mexameter®, Skin-Colorimeter, Tewameter®
SPREADABILITY, ANTI-GREASINESS/STICKINESS, FRICTION REDUCING: Frictiometer, Sebumeter®
NAIL HARDENING/THICKNESS/FLEXIBILITY, STRUCTURAL STRENGTH OF THE NAIL, ANTI-NAIL BREAKING: Nail StrainStress Meter, Tewameter® Nano
ANTI-PERSPIRANT: Tewameter®
WETTABILITY, SPREADABILITY, WATER-REPELLANCE: Drop Angle Meter
The devices for the skin type analysis derive from the scientific measurement methods known for many years and used all over the world for clinical studies and efficacy testing. However, the skin type analysis devices have a less accurate resolution. Example: they express the sebum content e.g. in "dry", "normal", "oily", whereas the scientific Sebumeter® shows the sebum content in a high precision figure to monitor even smallest changes in the sebum 
level.
Some systems for skin type analysis are available with an attractive, cosmetic software to recommend products and thus differ from the scientific measurement programmes. The cosmetic consulting devices are not used for clinical studies but for promotional use.
The software for the scientific laboratory devices possesses check calibration facilities and supports the statistical gathering of data for the evaluation of a study.
