UNISENSE SULFILOGGER User Manual page 29

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 S. Experience shows that this is not an easy task
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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 -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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