Owner manual

3.4 Multi-mode electrode (MME)

746 VA Trace Analyzer / 747 VA Stand

3-19

• Gently tap the MME with your finger and turn the slotted screw 9696 very

slowly clockwise until the mercury flow just stops. (The tapping action is

used to knock off the mercury drops so that it is easier to see whether

mercury continues to flow.)

• Finally, turn slotted screw 9696 a quarter of a turn clockwise.

Checking the MME for leaks

• Select dialog page "STAND" then switch on the dropping mercury elec-

trode by pressing the softkey <DME>. The mercury drops freely out of the

capillary for ca. 1 min.

• Press softkey <HMDE>. A single mercury drop is formed. Knock this off by

gently tapping the MME 3838 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 9696 still further in a clock-

wise direction and repeat check.

3.4.5 Filling the capillary using vacuum

Filling of the glass capillary 109109 with vacuum is advisable in all cases where diffi-

culties have been found with the method without vacuum described in section

3.4.4. Filling with vacuum is especially recommended when no ultrapure Hg is

available.

To fill the mounted glass capillary 109109 (section 3.4.3) with Hg with vacuum, pro-

ceed as follows:

Set up filling station

• All actions involving the electrode and the mercury vessels must be

performed in or over the drip pan 113113 supplied (see Fig. 14).

• The MME 3838 is placed in the electrode holder 114114 for filling.

Connection for vacuum pump

• For filling the capillary 109109, the filling tubing 115115 is required. At one end it

is fitted with a filling cone 116116 for mounting on the capillary 109109, and at

the other end with the tubing coupling 118118 for attachment to the line for

the vacuum pump.

• To avoid possible mercury losses, two gas wash bottles 117117 are attached

to the filling tubing 115115.

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.

Mount filling tubing

• Mount filling tubing 115115 with filling cone 116116 on glass capillary 109109.

• Connect filling tubing 115115 with tubing coupling 118118 to the two gas wash

bottles 117117 and the vacuum pump (see Fig. 14).