Metrohm 797 VA Computrace - Manual (Page 49)

3.1 Electrodes
797 VA Computrace – Software
37
Voltage step time
t
Hg drop
surface
Notes:
•
In the exploratory mode, the DME can be used for the meas-
urement modes DC, NP, DP and AC. In the determination mo-
de, the DME can be used for the measurement modes DP and
AC.
• An advantage of the DME compared with the SMDE is that the
MME capillary is subjected to less mechanical stress.
• A disadvantage of the DME compared with the SMDE and
HMDE is the higher mercury consumption and the lower sensi-
tivity as the electrode surface constantly changes during the
measurement phase.
SMDE
SMDE is an electrode mode of the Multi-Mode Electrode and
stands for Static Mercury Drop Electrode. It combines the fea-
tures of the DME and the HMDE: as with the DME, the mercury
drops are constantly renewed, but during the measurement the
drop surface is constant as in the HMDE case. Each mercury drop is
knocked off by a tapping mechanism after the
Voltage step time
set in the measurement mode.
Drop size [ 1...9 ; 4 ]
Size of the mercury drop (surface 0.15 mm 2 ...0.60 mm 2 ).
t
Voltage step time Drop size
× 40 ms
Hg drop
surface