3 Installation
757 VA Computrace – Hardware
24
2 Draw up mercury
•
Attach needle
91
to syringe
90
.
•
Draw up 6 mL ultrapure mercury slowly and carefully using syringe
90
.
3 Add mercury to MME
•
Lower syringe needle
91
into the top opening of the MME
17
between
sealing ring
85
and sealing needle
76
.
•
Expel mercury slowly and carefully from the syringe to allow it to flow into
the Hg reservoir
82
.
The Hg reservoir
82
must never be filled more than
2
/
3
full with mer-
cury.
3.3.3
Mounting the capillary
The glass capillaries
88
for the multi-mode electrode
17
are supplied separately in
a protective plastic package. After they have been unpacked, avoid any contact
whatsoever with the sensitive capillary tip. The capillary
88
is mounted in the MME
filled with mercury as described in
section 3.3.2
as follows:
1 Insert retaining nut
•
Screw retaining nut
87
into screw thread
83
until a slight resistance is
noticeable (on no account screw in retaining nut fully!).
2 Insert capillary
•
Cut open plastic package containing the glass capillary
88
on the side of
the large capillary opening using scissors (do not tear open), leave capil-
lary in the package.
•
Insert glass capillary
88
directly from its protective plastic package
through the retaining nut
87
into the sealing ring
85
and push in as far as
it will go.
3 Tighten retaining nut
•
Firmly tighten retaining nut
87
by hand (do not use a tool). The glass
capillary
88
should then be centered in the opening of the retaining nut
87
.
•
If this is not the case, undo retaining nut
87
by one full turn and then
retighten by hand. When tightening, move glass capillary
88
in a circle so
that it is centered in the feedthrough of the retaining nut
87
.
3.3.4
Filling the capillary without vacuum
The glass capillary
88
can normally be filled with mercury by the method described
here without vacuum. However, if difficulties regarding stability or reproducibility
arise with a capillary filled in this manner, try to fill the capillaries by the alternative
method with vacuum (
section 3.3.
5).
To fill the mounted glass capillary
88
(
section 3.3.3
) with Hg without vacuum, pro-
ceed as follows:
