Owner manual
3.4 Multi-mode electrode (MME)
746 VA Trace Analyzer / 747 VA Stand
3-25
3.4.9 Cleaning the MME
If the mercury in the multi-mode electrode is contaminated and this leads to distur-
bances (see sections 7.4.2 and 7.4.3), the MME must be cleaned and refilled with
ultrapure mercury. Proceed as follows:
1
Remove multi-mode electrode from 747 VA Stand
• Unscrew FEP tubing 5151 and 5959 from the MME, disconnect electrode
cable 3737 from MME.
• Take multi-mode electrode 3838 out of measuring head 4141 while gently
tapping the MME to knock off any mercury drops on the glass capillary
into the measuring vessel.
2
Remove old mercury
• Place multi-mode electrode 3838 in a horizontal position in the electrode
holder 114114 (see Fig. 15-3). The slotted screw 101101 is now at the top.
• Unscrew slotted screw 101101 using a suitable coin.
• Carefully turn MME and empty mercury through the threaded opening
100100 into a waste container placed in the drip pan 113113. While doing so,
gently tap the glass capillary 109109 and the MME to ensure that all mercury
flows out of the MME.
3
Dismantle MME
• Unscrew retaining nut 108108.
• Take glass capillary 109109 out of opening 104104, the sealing ring 106106 and the
locking ring 107107 are removed at the same time. Remove these two parts
from the glass capillary 109109.
• Remove insert ring 105105 from the MME.
• Unscrew slotted screw 9696 with a suitable coin in an anticlockwise direc-
tion from screw thread 9898.
• Screw locking ring 9595 onto slotted screw 9696 and pull out of the MME.
4
Dispose of old capillary
• Connect filling tubing 115115 with the tubing coupling 118118 to the two gas
wash bottles 117117 and the vacuum pump (see Fig. 14).
• Insert glass capillary 109109 (capillary end) in the filling cone 116116 of the filling
tubing 115115.
• Remove mercury from the capillary with the vacuum pump.
5
Clean MME
• Clean inner compartments of the MME, contact pin 102102 and the screw
threads 9898, 100100 and 104104 with a lint-free cloth.
• Thoroughly rinse all inner compartments of the MME and the unscrewed
individual parts with dist. water and then dry with N
2
.
Do not use any organic solvents.