Metrohm 746 VA Trace Analyzer - Manual (Page 91)

4 Introduction to the operation
746 VA Trace Analyzer / 747 VA Stand
4-6
4.1.4 Tests to check the 747 VA Stand
The tests described below are used to check the functions of the 747 VA Stand
such as purging, stirrer, DME and HMDE required for the illustrative methods. Per-
form the tests as follows (if the 746 VA Trace Analyzer is switched on, you can start
directly with point 2):
1 Switch on instrument
• Switch on the 746 VA Trace Analyzer with mains switch 11 11 at the rear of
the instrument. The instrument is initialized. If all is in order and the 747
VA Stand is attached properly, the dialog page "MONITORING" appears
after a few seconds.
2 Switch to dialog page "STAND"
• Press the yellow key. The "STAND" dialog page appears:
747 VA STAND
Manual Address 1
Switches Settings States
ДДДДДДДДДДДДДДД ДДДДДДДДДДДДДДД ДДДДДДДДДДДДДДДДДДДДДД ДДДДДДДДДДДДДДДДДДДДДД ДДДДДДДДДДДДДДДДДДДДДДДДД ДДДДДДДДДДДДДДДДДДДДДДДДД
Pressure off U.standby --- mV
Purging off
Stirrer off Rot.speed 2000 /min
DME off
HMDE off Drop size 5
SMDE off Drop size 5
RDE off Rot.speed 2000 /min
V.meas max 80 mL
Pressure Purging Stirrer DME HMDE SMDE RDE >>
Settings
3 Testing purging
• To check the inert gas purging at the 747 VA Stand, the measuring
vessel must be filled with ca. 20 mL dist. water.
• Press the softkey . The inert gas purging is switched on, at
the same time the displays for Pressure and Purging switch to on and
an asterisk * appears in the two softkeys of the same name.
• Check whether the purging of the analysis solution functions properly. If
so, you can switch off the purging by pressing the two softkeys
and .
• If the purging does not function properly, check the inert gas connection
as described in section 3.3.3 and then repeat the test.
The purging with inert gas (e.g. N
2
) serves to remove any electrochemically active
and hence interfering atmospheric oxygen in aqueous solutions. In determinations, the
instructions PURGE or TPURGE are used for this with a purging time of 3
…5 min
generally sufficing (see section 5.7.3).