The Tewameter® TM 300 is the worldwide most accepted measuring device for the assessment of the Transepidermal Waterloss (TEWL). This is an indispensable parameter for the evaluation of the water barrier function of the skin and a basic measurement in all kind of applications. Even the slightest damage in the skin water barrier can be determined at an early stage. Several hundreds of international scientific studies demonstrate its importance in dermatological research and cosmetological fields.
A certain evaporation of water from the skin takes always place as part of the normal skin metabolism. As soon as the barrier function of the skin however is slightly damages, the waterloss will increase (even with smallest damages invisible to the human eye). Therefore this measurement is a basis for all cosmetic and dermatological research. The Tewameter® probe measures the density gradient of the water evaporation from the skin indirectly by the two pairs of sensors (temperature and relative humidity) inside the hollow cylinder. This is an open chamber measurement. The open chamber measurement method is the only method to assess the TEWL continuously without influencing its micro environment. A microprocessor analyses the values and expresses the evaporation rate in g/h/m2.
A = surface [m2]
m = water transported [g]
t = time [h]
D = diffusion constant [= 0.0877 g/m(h(mmHg))]
p = vapour pressure of the atmosphere [mm Hg]
x = distance from skin surface to point of measurement [m]
The measurement of the TEWL and the quality of the barrier function of the skin is the basic measurement for all cosmetic applications.
The sensors of the probe normally have room temperature (20-22°C), whereas skin temperature is 30°C and higher. As the amount of evaporating water measured with the device is extremely small (healthy skin 8-15 g/h/m² → 0.000001333 - 0.00000025 g/minute/cm²), the sensors inside the probe should reach skin temperature to measure this small amount exactly and stable. With the probe heater the probe head is constantly warmed up to a temperature close to skin temperature and thus getting very quickly accurate and stable results.
|sensors inside the probe cold (room temperature)||
sensors preheated to 30°C -
stable measurement in an extremely short time
With the Invitro Tewameter® VT 310 a probe for the TEWL measurement is available, which offers all benefits of the Tewameter® and is perfectly suited to sit on a Franz cell. It emulates completely the upper part (donor chamber) of a Franz cell (standard is 15 mm Ø, other sizes on request).Thus the probes sits exactly on the membrane of the Franz cell as it would sit on skin directly without needing further adapters.The measured TEWL-value is expressed in g/h/m², the worldwide acknowledged absolute measuring value for skin.
There are specials adapters available for the probe.
One adapter with smaller opening is available for different applications e.g. measurement on small animals or small skin sites (reduced the measurement area to 2 mm Ø).
Special steel rings are available when measuring on special surfaces. They can be mounted on the measuring head and after the measurement taken off the probe and be disinfected.
Other related probes avaialble:
TEWL measurement probe with three measurement chambers, the Tewameter® Triple TM 330T.
Invitro Tewameter® VT 310 to measure directly on Franz cells
Please also read Frequent Asked Questions on the Tewameter®.
Dimensions: Measuring Chamber: 2 cm, Ø 1 cm, Probe: 15.3 cm, Cable length: approx. 1.3 m, Weight: 90 g, Resolution: Humidity: ± 0.01 % RH, Temp.: ± 0.01 °C, TEWL: 0.1 g/h/m²
Accuracy for TEWL-values lower than 70 g/h/m²:
rel. humidity (r.h.): ± 1.5 % for r.h. between 30 % and 90 %, ± 2.5 % for r.h. between 90 % and 100 % and for r. h. between 10 % and 30 %
Waterloss: ± 0.5 g/h/m² for r.h. ≥ 30 %; ± 1.0 g/hm² for r.h. ≤ 30%,
Temperature: ± 0.5 °C
Probe Heater PR 100: Power supply: external 100-240 VAC, 47-63 Hz, DC 12V/4A, Dimensions: 10 x 11 x 10.5 cm Weight: 470 g
Operating conditions: T: 10-40° C r.H.: 30-70 % RH,
For the dimensions, etc. of the wireless probes, please see the technical data of the basic devices.
Technical changes may be made without prior notice.