Yokogawa EXAxt SC450 4-Wire Analyzer for Conductivity/Resistivity - Manual (Page 62)

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IM 12D08N05-01E
SC42-EP04 cc = 10 cm -1 2-electrode sensor
This sensor is in the program for historical reasons. It makes little sense to select this sensor for
new applications.
It was used mostly for process water and light process solutions. The operating range can be 1to
100 mS/cm with higher readings having a very high risk of polarization. The SC42-EP18 or the
SC42-EP08 (4-el sensors) covers these ranges with much greater certainty of avoiding polariza-
tion.
SC42-EP08 cc = 10 cm -1 4-electrode sensor
Process applications are where this sensor is used, including light fouling. The best range of ap-
plication is 1mS/cm to 500mS/cm. The four-electrode system copes with some contamination from
the process, and eliminates the tendency for polarization to occur at the higher conductivity. The
upper limit is determined more often by chemical compatibility. The epoxy material is attacked
by many of the chemicals that are present in high conductivity solutions. It is better suited to flow
through installations in FS40 and FF40 adapters and fittings, but it can also be used in dip tubes -
FD40.
SC42-TP08 (FP08) cc = 10 cm -1 4-electrode sensor
These sensors are for extreme applications. The PTFE or the PVDF used for the body of the sen-
sor gives good chemical resistance for the strongly corrosive applications. These sensors are
intended for use in ranges 10mS to 1000mS/cm. Careful selection of the holder is needed. The
PVDF sub-assembly is an obvious choice for the SC42-FP08, and the PP flow fitting often has suf-
ficient corrosion resistance for the application. In any case selection must be done with due regard
to the process conditions.
The 2-electrode versions (SC42-T(F)P04 do exist, but like the epoxy version (SC42-EP04) they
should be discounted for new applications.