Maintenance; Calibration - Cortexa Technology DermaLab Mini Instructions For Use Manual

Pressing (A) toggles between normal and extended view. Detailed settings are only shown in ex-
tended view. Touching the Sample button initiates the TEWL measurement, and the graph for the
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TEWL is shown in g/m
40 sec., the measurement stops automatically upon reaching a preset stop-criterion (F). Several
stop criteria can be active at the same time. A green color will indicate which stop criterion
stopped the measurement. The stop-criteria includes a preset standard deviation, a preset time,
or linearity of the vapor gradient (slope target). By default, the stop-criterion is set to a standard
deviation of 0.2.
In rare cases, where the standard deviation during the measurement does not exceed the preset
stop-criterion due to very low evaporation (indicated by a fully horizontal curve), the automatic
stop function will not be activated. If so, the measurement can be stopped by pressing Stop.
The TEWL main result is presented as the mean value over the last 5 seconds. In normal view,
the history of the last measurements is shown (E). This makes it more convenient to do several
measurements on the same subject.
In the extended view, the sensor data and absolute humidity are shown for all 5 layers (I). Se-
lected data is visualized (G) by clicking on the desired parameters (H). These sensor values form
basis for the calculation of TEWL and may provide useful information.
The environmental conditions are shown on the screen. Initially, they are measured by the layer 5
sensors when entering the TEWL screen. It is possible to make a new measurement by pressing
"Measure Ambient" (D). The Clear last result button deletes the last measurement while clear all
results clears all measurements.

13.4 Maintenance

There is no maintenance associated with the use of the TEWL module besides cleaning. To clean
the probe front, simply wipe it off using a dry cloth. Should more thorough cleaning be necessary,
a drop of alcohol may be applied to the cloth. However, care should be taken not to touch the sen-
sors inside the measurement chamber.
The sensors inside the probe shall not get in close contact with volatile chemicals such as sol-
vents or other organic compounds. Especially high concentration and long exposure must be
avoided. Ketenes, Acetone, Ethanol, Isopropyl Alcohol, Toluene, etc. are known to cause drift of
the humidity reading – irreversibly in most cases. Strong acids or bases, ozone in high concentra-
tion, or H O may affect the sensor irreversibly. Applying cleaning agents directly to the sensors
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inside the measurement chamber may lead to drift of the reading or complete breakdown of the
sensor.
The sensors show best performance when operated within the temperature and humidity range of
5 °C – 60 °C and 20 %RH – 80 %RH, respectively. Long-term exposure to conditions outside this
range, especially at high humidity, may temporarily offset the RH signal (e.g. +3%RH after 60h
kept at >80%RH). After returning to the normal temperature and humidity range the sensor will
slowly come back to calibration state by itself. Alternatively, a re-conditioning procedure can be
used: (80-90°C [176-194°F] at < 5%RH for 24h (baking) followed by 20-30°C [70-90°F] at > 74
%RH for 48h (re-hydration). Prolonged exposure to extreme conditions may accelerate ageing.

13.5 Calibration

The probe sensors may, depending on use, need re-calibration at regular intervals. To ensure the
best performance and interchangeability of your probe, it is strongly recommended to return
probes for factory re-calibration regularly. When doing so, both the humidity and temperature
sensors are calibrated in a climate chamber that has been calibrated in an ISO/IEC 17025
accredited calibration laboratory (NIST traceable).
/h as a function of time. After the TEWL has stabilized after typically 30 –
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