Metrohm 797 VA Computrace - Manual (Page 150)

5 Determination mode
797 VA Computrace – Software
138
Working method
Printout of the method parameters of the working
method in the working memory.
Order [ 1...6 ; ]
Order of printout for the element.
Sample table
Printout of the sample table.
5.8 Data processing and evaluation
Data transfer
After the start of a determination, the parameters of the current
working method are copied into the determination method. The
parameters necessary for the VA measurement are then sent from
the PC to the VA Computrace via USB connection. The data acqui-
sition at the VA Computrace stand is started and controlled by the
internal processor, which receives and stores the measurement
data. At the end of each voltammogram, the recorded data are
sent back to the PC where they are evaluated and saved in a de-
termination file.
Data acquisition
The 797 VA Computrace stand operates according the potentio-
static, 3-electrode principle in which the voltage of the working
electrode is controlled with the aid of a virtually currentless refer-
ence electrode to the preset desired value and the current flows
across a separate auxiliary electrode. The voltage drop in the ana-
lysis solution is automatically compensated. Measurement of the
current with digitalization involves automatic matching of the am-
plifier sensitivity to the latest measured value so that measurements
are always performed with optimum accuracy.
The type of measured value recording, the measurement range and
the measurement frequency are defined by the selection of elec-
trode, VA measurement mode and the corresponding sweep pa-
rameters. The following combinations of
electrode and VA mea-
surement mode are possible:
DC NP DP SqW AC CV PSA CCPSA CVS CPVS
DME (•) (•) • •
SMDE (•) (•) • •
HMDE • (•) • • • • • • •
RDE • (•) • • • • • • • •
(•) This combination can only be used in the exploratory mode.
The measured value pairs recorded per single measurement sweep
are stored in data blocks characterized by the VR number (variation