Myron L PS9TK - Manual (Page 59)

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method that ignores fill level, electrolysis, electrode characteristics, etc.,
and features a microprocessor to perform temperature compensation.
In simpler instruments, conductivity values are usually assigned an
average correction similar to that of KCl solutions for correction to
25°C. The correction to an equivalent KCl solution is a standard set
by chemists that standardizes the measurements and allows calibration
with precise KCl solutions. In the P
OOL
P
RO
, this correction can be set to
other solutions or tailored for special measurements or applications.
B. Tempco Variation
Most conductivity instruments use an approximation of the temperature
characteristics of solutions, perhaps even assuming a constant value.
The value for KCl is often quoted simply as 2%/°C. In fact, KCl tempco
varies with concentration and temperature in a non-linear fashion. Other
solutions have more variation still. The P
OOL
P
RO
uses corrections that
change with concentration and temperature instead of single average
values. See Chart 1.
C. An Example of 2 different solution selections and the
resulting compensation
How much error results from treating natural water as if it were KCl at
15°C?
A tap water solution should be compensated as 442 with a tempco of
1.68 %/°C, where the KCl value used would be 1.90 %/°C.
Suppose a measurement at 15°C/59°F is 900 microsiemens of true
uncompensated conductivity.