YOKOGAWA SC150, Instruction Manual

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IM 12D7B4-E-H
42
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 polarization.
SC42-EP08 cc = 10 cm
-1
4-electrode sensor
Process applications are where this sensor is used, including light fouling. The best range
of application 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 sensor 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 sufficient corrosion resistance for the application. In any case
selection must be done with due regard to the process conditions.
0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000
1
2
3
4
Cell Constant
0.01 cm
0.01 0.1 1.0 10 100 1000
µ
S/cm
Under useful
range
Useful
range
Use 4-el
sensor
-1
Cell Constant
0.1 cm
-1
Cell Constant
1.0 cm
-1
Cell Constant
10 cm
-1
mS/cm
The 2-electrode versions (SC42-T(F)P04 do exist, but like the epoxy version (SC420-EP04)
they should be discounted for new applications.