UNISENSE HYDROGEN SENSOR, User Manual

Page: 12 / 24

12
For a Unisense CAL300 calibration chamber,
5 minutes of bubbling at a rate of 5 l per
minute is sufficient time to achieve 99 % of
the concentration . If the equipment (gas
mixture controller) is available, this method
can be convenient, as you can switch
between different constant hydrogen
conditions without changing the water .
Use the solubility table (Table 1) to find the
correct mixture at temperatures other than
20 °C . To obtain correct concentrations,
the headspace above the water in the
calibration chamber must be closed except
for a hole only slightly larger than the
microsensor shaft . This effectively prevents
ambient air from entering the vessel .
We recommend the CAL300 Calibration
Chamber for calibrations .
2 . Add a defined volume of hydrogen-
saturated water to a defined volume of
water in a calibration chamber . For instance,
1 ml of H
2
saturated water contains 0,805
µmol at 20 °C (see Table 1), and to obtain
water with a hydrogen concentration of
10 µM, 3 .08 ml hydrogen-saturated water
should be added to a total volume of 246,9
ml hydrogen free water in the calibration
chamber . After the addition of hydrogen-
saturated water to the calibration chamber
mix it thoroughly by moving the sensor
in its protection tube up and down for a
few seconds and read the signal when it is
stable . Do not stir bubbles into the water
or mix by bubbling, as this will remove
hydrogen from the water . A magnetic stirrer
is not recommended as a mixing tool as a
WARNING
Vigorous bubbling
water with any
gas may cause
the water to cool
considerably.
Monitor the
temperature to
find a suitable
bubbling rate,
which does not
cool the water
significantly.
Calibration
chamber CAL300