6.1 List of faults
￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
78
￭￭￭￭￭￭￭￭
884 Professional VA
Problem
Cause
Remedy
Dripping stops prematurely
(only for HMDE).
￭
The stirrer hits the capillary: Check the posi-
tion of the MME pro and the capillary.
￭
Nitrogen bubbles rise up when the Hg
drips: Check the position of the gas inlet
tubing and correct if necessary.
￭
Capillary defective: Replace the capillary
(see the
Multi-Mode Electrode pro docu-
ment (8.110.8018XX)
).
The drop size is not repro-
ducible.
￭
The capillary and/or needle is not adjusted
correctly: Adjust the needle and capillary
(see the
Multi-Mode Electrode pro docu-
ment (8.110.8018XX)
).
￭
The capillary and/or needle is defective:
Replace the capillary and needle. If neces-
sary, clean the MME pro (see the
Multi-
Mode Electrode pro document
(8.110.8018XX)
.
￭
The tapping mechanism is not functioning
correctly: Check the tapping of the drops.
6.1.3
884 Professional VA for CVS
Problem
Cause
Remedy
Conditioning takes a
long time.
The reference electrode has
not yet reached equili-
brium.
After maintenance of the reference electrode,
wait for at least 20 min before starting a meas-
urement.
The working electrode is
contaminated.
Condition the working electrode in pure VMS.
The electrode tip of the
working electrode has
been in use for a long
period.
￭
Immerse the electrode tip in c(NaOH) = 0.5
mol/L for approx. 10 min and then thor-
oughly rinse with distilled water.
￭
Replace the electrode tip if necessary.
VMS is contaminated.
Check the purity of the reagents (only reagents
of sufficient purity, i.e. > 99%, should be
used).
The water quality is poor.
Use distilled water, type-II grade (ASTM
D1193-91) or higher.
Summary of Contents for 884 Professional VA
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