IM 12A06S01-00EN-P
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reference temperature setting, a linear compensation function is obtained, which is suitable
for all kinds of chemical solutions.
•
NaCl
This method uses the standard temperature compensation function based on a sodium
chloride (NaCl) solution. This function can be used for various applications and is compatible
with the NaCl compensation function of typical laboratory or portable instruments.
•
Matrix
This is compensation which uses the temperature compensation matrix. The temperature
compensation matrix is a table of conductivity values at various temperatures and various
concentrations of a specific solution. The measured conductivity is compensated based on
this matrix to the conductivity at the reference temperature.
It is possible to select from a list of 12 predefined matrices, or create up to 2 user defined
matrices by using HOST system. For details see Appendix 5.
The compensation is active up to 10°C and 10% outside the values given in the matrix
table. In this case the temperature compensation is performed by extrapolation of the matrix
values. When temperature or pre-compensated value is outside this deviation range, no
calculated value will be generated.
7.1.5 Concentration
The concentration is a calculation from a known conductivity value related to a specific
concentration of the process. This concentration calculation can be done using a matrix
table or by linear interpolation using a concentration table.
The choice for which calculation method is used can be set by HOST system.
7.1.6 USP23
USP stands for United States Pharmacopeia, and is basically a conductivity monitoring
system to meet USP23 regulations in the Pharmaceutical Industry.
The USP limit is based upon the predefined uncompensated conductivity values at a certain
process temperature as directed by USP<645>. For details see Appendix 6.
If the uncompensated measured conductivity value at process temperature is more than the
USP limit value, a USP limit warning is flagged.
To warn the user for an upcoming USP error, a USP margin can be set. This USP margin is
set as a percentage of the USP limit. In case the uncompensated conductivity value is within
this USP margin, a USP margin warning will be flagged. The HOST system can act in a
proper way on these warning flags.
7.1.7 SC settings
The conductivity/resistivity is the result of the measurement with a specific conductivity
sensor.
There are two (2) types of sensors which can be set:
•
2-electrode
, usually used for conductivity and/or resistivity measurements.
•
4-electrode
, meant to measure at high conductivity ranges where polarization of the
electrodes may cause an error in conductivity measurement.
Sensors have a so-called cell constant (c.c.) which is defined by the mechanical structure of
the sensor (length in between the electrodes divided by the surface of the electrode), which
can be set in the unit cm-1 or m-1. The process values will be expressed in S/cm or S/m in
conductivity mode, and Ω.cm or Ω.m in resistivity mode.