Conductivity Measurement Settings - Mettler Toledo SevenCompact S230 Instrucciones De Manejo

6.4 C onductivity measurement settings
Reference Temperature
Two reference temperatures are available:
20 °C (68 °F) and 25 °C (77 °F).
Temperature Correction
There are four options:
●
linear
●
non-linear
●
pure water
●
off
With most solutions, a linear interrelationship between conductivity and temperature is given. In
such cases, select the linear correction method.
The conductivity of natural water shows strong non-linear temperature behavior. For this reason,
use the non-linear correction for natural water.
The option pure water should only be used for cases in which ultra-pure or pure water is mea-
sured.
In some cases, for example, when measuring according to USP/EP (United States/European Phar-
ma c opoeia) you need to switch off the temperature correction. This can also be done by entering a
lin e ar temperature correction factor of 0 % / °C.
- Linear
When selecting linear correction, the input window for the temperature correction coefficient (0.000
– 10.000 % / °C) appears.
The measured conductivity is corrected and displayed using the following formula:
●
GT = GT / (1 + ( α (T – T
Ref
GT: conductivity measured at temperature T (mS/cm)
GT : conductivity (mS/cm) displayed by the instrument, calculated back to the reference tem p er-
Ref
a t ure T
Ref
: linear temperature correction coefficient (%/°C);
α
T: measured temperature (°C)
T : Reference temperature (20 °C or 25 °C)
Ref
Each sample has different temperature behavior. For pure salt solutions the correct coefficient can
be found in literature, otherwise you need to determine the
tiv i t y of the sample at two temperatures and calculate the coefficient by using the formula below.
●
= (GT1 - GT2) * 100% / (T1 - T2) / GT2
α
T1: Typical sample temperature
T2: Reference temperature
GT1: Measured conductivity at typical sample temperature
GT2: Measured conductivity at reference temperature
- Non-linear
The conductivity of natural water shows strong non-linear temperature behavior. For this reason,
use the non-linear correction for natural water.
The measured conductivity is multiplied by the factor f
dix") and thus corrected to the reference temperature of 25 °C:
)) / 100 %)
Ref
= 0: no temperature correction
α
for the measured temperature (see "Appen-
25
-coefficient by measuring the con d uc-
α
Menus and settings 29