Mettler Toledo SevenGo Duo pro SG78 Instrucciones De Manejo página 28

Menus and settings
2. Customized conductivity standard
For those who use their own conductivity standard for calibration of the conductivity sensor, the con duc-
tiv i ty of the calibration standard (in mS/cm) can be entered in this screen. Up to 5 temperature-dependent
val ues can be entered in the table.
Lowest possible special standard: 0.00005 mS/cm (0.05 µS/cm).
This value corresponds to the conductivity of natural water at 25 °C, exclusively caused by the auto pro-
tol y sis of water.
When switching from a predefined standard to customized standard, you should always save the table
even if there are no changed values.
3. Cell constant
If the cell constant of the conductivity cell being used is accurately known, it can be entered directly in the
meter.
a) Select Enter Cell Constant in the menu.
b) Press CAL in the measurement display.
2. Calibration Reminder
For a full description, see "pH/ion calibration settings."
6.7 Conductivity measurement settings
1. Reference Temperature
Two reference temperatures are available: 20 °C and 25 °C.
2. Temperature Correction
There are three options:
●
linear
●
non-linear
●
off
With most solutions, a linear interrelationship between conductivity and temperature is given. In such
cas es, 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.
In some cases, for example, when measuring according to USP/EP (United States/European Phar ma-
copoeia) you need to switch off the temperature correction. This can also be done by entering a linear
tem per a ture 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 + ( (T – T
Ref
Definitions
●
GT = conductivity measured at temperature T (mS/cm)
●
GT
Ref
ture T
●
= linear temperature correction coefficient (%/°C);
●
T = measured temperature (°C)
●
T
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 -coefficient by measuring the conductivity of the
sam ple at two temperatures and calculate the coefficient by using the formula below.
24
The request to enter the cell constant appears.
))/100 %)
Ref
= conductivity (mS/cm) displayed by the instrument, calculated back to the reference tem per a-
Ref
= Reference temperature (20 °C or 25 °C)
= 0: no temperature correction
pH/ORP/Ion/Conductivity meter SG78