Metrohm 757 VA Computrace - Manual (Page 41)

3.5 Reference electrode
757 VA Computrace – Hardware
37
3.5.2 Startup procedure
The reference electrode 22 is supplied in modular form as the reference system
101 and the electrolyte vessel 102 and has first to be filled and assembled as fol-
lows:
1 Add internal electrolyte
Filling of the reference system is necessary only when the optional
6.0728.010 Reference system supplied dry is used, if the internal electrolyte
solution has to be renewed or if gas bubbles interrupt the electrical connec-
tion.
• Hold reference system 101 so that diaphragm 108 faces upwards.
• Unscrew diaphragm support 107.
• Fill electrolyte compartment 106 completely with the desired internal
electrolyte. Expel any air bubbles by tapping shaft gently.
• Screw diaphragm support 107 back on, the electrolyte solution thus
displaced is expelled through the vent opening 104.
2 Add bridge electrolyte
• Fill internal compartment 110 of the electrolyte vessel 102 with a suitable
bridge electrolyte whose composition depends on the analyses to be per-
formed (aqueous or non-aqueous solution, composition of the supporting
electrolyte, etc.).
If you use the same solution for the bridge electrolyte and the internal
electrolyte (single-junction operation), the inner diaphragm 108 can
be omitted to reduce the electrical resistance: Unscrew diaphragm
support 107 with diaphragm 108 from the reference system 101.
3 Screw reference electrode together
• Insert the filled reference system 101 in the vessel 102 filled with bridge
electrolyte and screw tight. The electrolyte solution thus displaced is ex-
pelled through the vent opening 109.
4 Install reference electrode in 757 VA Computrace Stand and
connect
• Insert reference electrode 22 in opening 58 of the measuring head 20
(see Fig. 6).
• Attach electrode cable 27 (RE) to reference electrode 22:
push cable lug under the screw and then tighten screw firmly.
• Turn reference electrode 22 so that the electrode cable 27 points to the
rear and not to the side (in the latter position it may become kinked and
damaged when cover 1 is closed).
• Wait approx. 20 min before first measurement (it takes some time for a
new reference electrode to become wet).