What
is the operating principle
of the VapoMeter?
The VapoMeter is
equipped with a closed cylindrical chamber that contains sensors for
relative humidity and temperature. The figure below shows a linear
increase of relative humidity (RH%) in the chamber shortly after
placing the device in contact with the skin. The TEWL is calculated
from the increase in RH%.
How do I know that the VapoMeter is ready
for next measurement?
The time between
measurements is automatically controlled. Relative humidity in the
chamber has to decrease back to ambient RH level, before the VapoMeter
is ready for next measurement. The ventilation period is longer after
high values (after 10 g/m²h about 10 seconds and after 100
g/m²h about 60 seconds).
How
long is the measurement time with
the VapoMeter?
A measurement with the
VapoMeter takes 7 to 16 seconds with the standard adapter and 9 to 34
seconds with the nail adapter. The measurement time is automatically
controlled and shown on the display; the higher the TEWL, the shorter
the measurement time. At the level of 10 g/m²h the measurement
time is 10 seconds with the standard adapter and 20 seconds with the
nail adapter. Under level 1 g/m²h with the standard adapter
and 2 g/m²h with the nail adapter the measurement time is 16
and 34 seconds respectively.
How does the VapoMeter differ from other TEWL meters?
The measurement principle of the VapoMeter differs
completely from the conventional devices in the market. It is a closed
chamber system that calculates the evaporation rate from the increase
of relative humidity in the measurement chamber. Compared with the open
chamber technique the measurement time is shorter, the device is
smaller and portable and ambient air flows do not disturb the
measurement. Continuous measurements are not possible, but since a
single measurement period is short, up to 2 measurements per minute at
low evaporation rates are possible.
Are there any scientific studies to
compare your device with other TEWL meters?
The VapoMeter has been compared independently with the Tewameter
(Courage & Khazaka, Germany).
We
have compared
the VapoMeter with Evaporimeter EP1 (Servomed, Sweden)
and Dermalab (Cortex Technologies, Denmark). The VapoMeter can measure
very high evaporation rates accurately.
What
is the accuracy of the VapoMeter?
Accuracy in measuring evaporation rate through a semipermeable membrane
is ± 10% (TEWL > 5 g/m²h) or 0,5
g/m²h (TEWL< 5 g/m²h). This is tested against
gravimetric evaporation rate (mass change of water samples covered with
vapour permeable membrane). The coefficient variation (CV), when
measured from water sample, is less than 6%. When measuring the skin,
the CV is typically less than 10%.
What is the possible measuring range?
The recommended measurement range is from 3 to 200
g/m²h, but the VapoMeter can measure evaporation rates beyond
these values. With the nail adapter values up to 300 g/m²h can
be measured.
How
is the VapoMeter calibrated?
The
VapoMeter is factory calibrated. Each calibration holds for up to 2
years unless the VapoMeter is used in very variable conditions or on a
daily basis continuously. We recommend recalibration since every other
year or once a year for units in heavy use.
The
calibration service is performed in specific conditions at the
manufacturing plant. Evaporation rates through semipermeable membranes
are measured at 3 different levels and at different RH conditions. The
water loss is calculated from the mass change of the water sample and a
VapoMeter is programmed accordingly.
How does the angle of the VapoMeter with respect to the
measurement site affect the measurement?
During the measurement the measured skin area has to be sealed by the
adapter. Apart from this the VapoMeter is orientation independent and
the angle of use does not affect the measurement values. This is due to
the closed chamber and the measurement principle.
What is the difference between the
standard and the nail adapter?
The
standard adapter has on opening diameter of 11 mm and it is designed
for use of normal skin sites. The standard adapter can be used for
values up to 200 g/m²h. The nail adapter's opening diameter is
4,5 mm and it is fitted with a silicone ring. It can be used for hard
surfaces like the nail or for other small difficult areas like the lip,
eyelid, armpit, etc. It is also recommended to use the nail adapter
when measuring very high evaporation rates, up to 300 g/m²h.
It is necessary to change the measurement mode of the VapoMeter when
changing between the standard and the nail adapter.
How do I clean and sterilize the
VapoMeter?
The VapoMeter may be wiped
clean with the soft cloth. Care should be taken not to touch the
sensors in the chamber. The adapters that are in contact with skin can
be sterilized separately by autoclave or ethanol.
For complete product information, use the contact form.
