Owner manual
3 Installation
757 VA Computrace – Hardware
26
5 Checking the MME for leaks
•
Switch on the dropping mercury electrode by selecting
DME
in the
COM-
PUTRACE CONTROL
window and clicking on . The mercury
drops freely out of the capillary.
•
Select
HMDE
and click on . A single mercury drop is formed.
Knock this off by gently tapping the MME
17
with your finger and check
that the mercury flow has really stopped. Repeat this operation several
times.
•
If mercury continues to flow, turn slotted screw
75
still further in a clock-
wise direction and repeat check.
•
If it is not possible to stop the mercury flow, both the glass capillary
88
and the sealing needle
76
have to be replaced (see
section 3.3.9
).
3.3.5 Filling the capillary using vacuum
Filling of the glass capillary
88
with vacuum is advisable in all cases where difficul-
ties have been found with the method without vacuum described in
section 3.3.4
.
Filling with vacuum is especially recommended when no ultrapure Hg is available.
To fill the mounted glass capillary
88
(
section 3.3.3
) with Hg with vacuum, proceed
as follows:
1 Set up filling station
•
All actions involving the electrode and the mercury vessels must be
performed in or over the drip pan
92
supplied (see
Fig. 10
).
•
The MME
17
is placed in the electrode holder
93
for filling.
2 Connection for vacuum pump
•
For filling the capillary
88
, the filling tubing
94
is required. At one end it is
fitted with a filling cone
95
for mounting on the capillary
88
, and at the
other end with the tubing coupling
97
for attachment to the line for the
vacuum pump.
•
To avoid possible mercury losses, two gas wash bottles
96
are attached
to the filling tubing
94
.
3 Vacuum pump
•
To draw up mercury a suitable vacuum pump is required (e.g. water jet
pump). The partial vacuum
∆
p
should be around 25 mbar.
•
A vacuum release tap must be installed at the vacuum pump or in the line
between the gas wash bottle and the pump for slowly releasing the vac-
uum.
4 Mount filling tubing
•
Mount filling tubing
94
with filling cone
95
on glass capillary
88
.
•
Connect filling tubing
94
with tubing coupling
97
to the two gas wash
bottles
96
and the vacuum pump (see
Fig. 10
).