Operating instructions

48 METTLER TOLEDO DE40/50/51 Density Meter
Functions
10.6.1 Daily Check
This check is used mainly to control the working condition of the instrument. Is the instrument
really clean and dry? Did the previous operator really clean the cell after measuring his sample?
Pressing the Check key will always activate a daily check, unless a periodic check is due (see
also section 10.7).
Normally deionized or bi-distilled water is used for this purpose. Of course any other solution
can be used that suites the purpose i.e. is readily and in abundance available as well as has
a stable and well known composition.
This example uses water as daily
check solution.
The results of this daily check are
not stored in the instrument. They
are just meant to check whether the
instrument is really ready for the
next measurement.
10.6.2 Periodic Check
This check is used mainly to verify whether a new adjustment of the instrument is necessary
or not. Every adjustment of the instrument means that the instrument settings are changed.
This can be dangerous if it is not done correctly because all the measurements afterwards
will be wrong.
Pressing the check key will start a periodic check only when such a test is due according to
the settings in section 10.7.1. When no periodic check is due it will start a daily check.
So instead of actually performing frequent adjustments we suggest to perform frequent
checks with an exactly known standard solution. As long as this periodic check is done
successfully, there is no need to adjust the instrument. The results of periodic check are read
automatically in the instrument. Should the periodic check fail, the operator should carefully
clean and dry the measuring cell and then repeat the periodic check. If it still fails, then the
instrument should be adjusted again: press the <Calib.> key and follow the instructions of the
instrument.
If the periodic check fails too often even after re-adjusting the instrument - like every second
or third time - then you should contact your local supplier for servicing and closer support.
This example uses toluene as
periodic check solution.
The results of this periodic check are
stored in the instrument. They can be
retrieved under Function "6. Periodic"
and "Show Check List".
< Set Check >
Check :Daily Periodic
Standard :[Water ]
Ref.Value :[ 0.99821]g/cm3
Tolerance :[ 0.00008]g/cm3
Exit :[Execute]
< Set Check >
Check :Daily Periodic
Standard :[Toluene ]
Ref.Value :[ 0.86683]g/cm3
Tolerance :[ 0.00002]g/cm3
Exit :[Execute]