Courage + Khazaka electronic GmbH

FAQ

Tewameter®

Tewameter hand neu

FAQ for the Tewameter®

What are the main benefits of the "open chamber" measurement?

What is the use of the probe heater?

What is the function of the zero calibration (Offset)?

How can I sterilize the measurement area?

Is the Tewameter® probe suitable for in vitro measurements?

Are adapters available to measure on small body sites/small animals?

Does the measurement angle matter?

How is the Tewameter® calibrated?

 

What are the main benefits of the "open chamber" measurement of the Tewameter®?

  • Extremely accurate and quick measurement of the TEWL without any influences of the micro climate of the skin (pressure, occlusion, temperature)TEWprinz
  • The small size of the probe head minimizes the influence of air turbulence inside the probe.
  • Its low weight has no influence on the skin structure and ensures easy handling.
  • No waiting time between the measurements
  • Traceable, sophisticated calibration of humidity, temperature and TEWL to g/h/m2
  • A stable measurement is achieved quickly; continuous measurements over longer periods are also possible depending on the application.
  • Worldwide most used TEWL measurement method (even approved in space!). Several hundreds of performed studies with the Tewameter® prove this fact.
  • Recording of the ambient conditions with the Ambient Condition Sensor RHT 100 to help to compare measurements taken at different times
  • The development of the measurement values and average and standard deviation over time are always visible. Display of r.h and °C separately for upper and lower sensor. Display of r.h and °C separately for upper and lower sensor
  • Special calculations i.e. SSWL (Skin Surface Water Loss - assessment of skin's water holding capacity after occlusion) are possible
  • With the open chamber measurement even  higher waterloss values can be detected accurately as no water is collected inside the probe
  • Accuracy of the probe can be checked anytime quickly
  • Offset function to compensate "aging effects" of the probe
  • Measurement with several probes at the same time possible (e.g. for the measurement of large areas or sweat studies)
  • Accessories for measurements on small skin areas, wounds etc. are available

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What is the use of the probe heater?

Probe heaterThe sensors of the Tewameter®-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.

Tewameter curve cold Tewameter curve warm
sensors inside the probe cold (room temperature)

sensors preheated to 30°C -

        stable measurement in an extremely short time

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What is the function of the zero calibration (Offset)?

The Tewameter® is a highly sensitive measuring tool, calculating smallest differences. These differences highly influence the output of the probe, the TEWL value. The resolution for the temperature measurement is 0.01°C and for the relative air humidity (r.H.) 0.01 %.
All electronic components always have a technically caused long-term drift. To achieve accurate results it is indispensable that a zero offset of the sensor has to be performed from time to time (especially before a mayor study) in order to compensate such drifts. The corrected values will be saved independently from the calibration data in the probe and will be overwritten with each new zero offset. The zero offset correction only influences the calculation of the TEWL. After the procedure it should be around zero in the check calibration cap. The temperature values and values for r.H. of the sensors are not influenced by the offset. Thus the quality of the complete probe can be considered before executing the offset. In case the difference is too high the probe may be defective, the offset cannot be executed and the service should be contacted.

tewsondstrilring

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How can I sterilize the measurement area?

We supply special rings to be mounted on measuring head. They are made out of metal and can be taken off the probe and be disinfected after the measurement.

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Is the Tewameter® probe suitable for in vitro measurements?

VT direkt membran close upYes, certainly!
There is even a special probe for this application available, the Invitro Tewameter® VT 310, 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.
No other probe offers this possibility.

If needed, the probe can also be used on a centerpiece of high quality Teflon, which fits exactly on the probe and the receptor chamber of the Franz cell without further fixing adapters. The thus measured TEWL has to be regarded relatively (no longer absolute figures as the distance between probe and membrane is changed).

VT probe VT mittelstück Invitro Tewameter mounted on centerpiece

In vitro TEWL measurements have a variety of different applications:

  • inexpensive pre-screening before in vivo tests (no ethic commission, no expensive volunteers)
  • only way to study skin permeability and dermal absorption necessary for safety and efficacy testing
  • in vitro tests are established in several worldwide acknowledged guidelines: WHO (World Health Organization), SCCS (Scientific Committee on Consumer Safety) and OECD (Organization for Economic Cooperation and Development.
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Are adapters available to measure on small body sites/small animal?

Yes, a special adapter with only 2 mm Ø is available on request.Tewameter adapter small

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Does the measurement angle matter?

Not so much. It is important that the short end of the probe head sits on the skin tightly. The Tewameter® TM 300 has evenTewameter angleWeltraummessungsuccessfully been used under the special condition of the ISS Space Station!

 

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How is the Tewameter® calibrated?

The Tewameter® TM 300 is ex works calibrated in a highly sophisticated process of temperature, humidity and gravimetrical TEWL balancing over 48 hours. The calibration procedure is well known, published and scientifically acknowledged.
You can check the accuracy of the sensors anytime quickly but we strongly recommend to have this sensitive probe recalibrated once per year in our factory!

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