Metrohm 773 pH/mV Simulator - Manual (Page 5)

1.3 Circuit diagram
773 pH/mV Simulator
3
2 Operation
Before you use the instrument for the first time you must insert the
batteries. The battery compartment is found on the bottom panel of
the instrument. Press the battery compartment tongue downwards
to open the compartment. Insert the 4 batteries (Mignon 1.5V-LR6)
according to the diagram in the battery compartment (take care that
the plus poles are in the correct position!).
The instrument switches itself off automatically after 50 minutes op-
eration.
In order to avoid incorrect measurements resulting from exhausted
batteries, the 773 pH/mV Simulator switches itself off when the volt-
age is insufficient. The batteries must then be replaced. The batter-
ies have a working life of approx. 1 to 2 years (depending on use).
Checking the pH
Microprocessor-controlled pH meters and titrators measure U/mV
and pH via the same analog measuring input as a potential value.
They then calculate the pH from it by using the pH calibration pa-
rameters and the temperature. The processor system is checked
each time that the instrument is switched on so that it is virtually im-
possible that this conversion could be incorrect and not be noticed.
This means that for microprocessor-controlled instruments only the
potential U/mV needs to be checked. Neither the pH nor the tem-
perature compensation requires checking. This has the advantage
that the calibration parameters do not need to be set to standard
values.