User Manual
Table Of Contents
output August 19, 2019 8:28 Page 23
concentrations vary. The accuracy should be stated on the bottle
or can be provided by the vendor. If judging the accuracy of the
SulfiLogger
™
sensor based on liquid phase measurements there
are various ways to do this, all of which are prone to higher de-
grees of uncertainty than the gas phase testing: One option is to
prepare a standard (stock solution) mixture with a known con-
centration of H
2
S. Experience shows that this is not an easy task
and that the concentration should continuously be checked with
laboratory equipment such as spectrophotometric methods. For
more information on this, please contact Unisense. Another op-
tion is to do grab sample analysis of wastewater and compare the
results of a sulfide analysis (e.g. Clines’ method) with the measure-
ment values of the SulfiLogger
™
sensor. Please be aware, though,
that standard sulfide analyses of wastewater grab samples mea-
sures the Total Sulfide and not only the Total Dissolved Sulfide. For
a comparison between the SulfiLogger
™
sensor measurements
and grab sample values it is thus needed to filter out any particu-
late sulfide of the samples, and it is necessary to do a
pH
-based
calculation of the total dissolved sulfide from the SulfiLogger
™
sensor signal. Furthermore, it should be noted that correct sam-
pling techniques and sample preservation should be conducted
with utmost care to avoid significant influences on the measured
sulfide concentrations in the grab samples. For further informa-
tion and guidance on procedures for liquid phase comparisons,
please contact Unisense.
Problem:
Even though the SulfiLogger
™
sensor has just been cali-
brated, the measurements are showing incorrect values.
Solution:
When calibrating the SulfiLogger
™
sensor it is impor-
tant that the procedure described in the Maintenance chapter
above is followed. Please refer to the relevant chapter, and if
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