3.3 Multi-mode electrode (MME)
757 VA Computrace – Hardware
31
3.3.8
Changing the capillary
Contamination of the glass capillary can necessitate its replacement. In such a
case, proceed as follows:
1 Remove multi-mode electrode from 757 VA Computrace
Stand
•
Unscrew FEP tubing
30
and
38
from the MME, disconnect electrode
cable
16
from MME.
•
Take multi-mode electrode
17
out of measuring head
20
while gently
tapping the MME to knock off any mercury drops on the glass capillary
into the measuring vessel.
•
Place multi-mode electrode
17
in a horizontal position in the electrode
holder
93
(see
Fig. 11-3
).
2 Unscrew slotted screw
75
•
Using a suitable coin, unscrew slotted screw
75
out of screw thread
77
until the contact surface of the black O-ring at the Plexiglas wall (thin,
black stripe) is just visible below the metal thread
77
.
3 Dismantle old capillary
•
Position multi-mode electrode
17
vertically in the electrode holder
93
(see
Fig. 11-1
).
•
Undo retaining nut
87
completely by turning anticlockwise and lift up until
the lower part of the glass capillary
88
with the wide opening is visible.
•
Gently tap the glass capillary
88
to knock off any residual mercury in the
wide opening into the MME.
•
Press the retaining nut
87
downward with one hand and with your other
hand take glass capillary
88
completely out of the mount.
4 Dispose of old capillary
•
Connect filling tubing
94
with the tubing coupling
97
to the two gas wash
bottles
96
and the vacuum pump (see
Fig. 10
).
•
Insert glass capillary
88
(capillary end) in the filling cone
95
of the filling
tubing
94
.
•
Remove mercury from capillary with the vacuum pump.
5 Replenish mercury if necessary
Proceed as described in
section 3.3.2
.
6 Mount new capillary
Proceed as described in
section 3.3.3
.
7 Fill capillary
Proceed as described in
section 3.3.4
or
section 3.3.5
.
