Metrohm 757 VA Computrace - Manual (Page 123)

5.8 Data processing and evaluation
757 VA Computrace – Software
113
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 Add-on board via TCP/IP connection or to the VA
Computrace Interface via USB connection. The data acquisition
at the VA Computrace Stand is started and controlled by the Add-
on board or VA Computrace Interface, which receive and store
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 determination file.
Data acquisition
The 757 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
analysis solution is automatically compensated. Measurement of
the current with digitalization involves automatic matching of the
amplifier sensitivity to the latest measured value so that meas-
urements 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
electrode, VA measurement mode and the corresponding sweep
parameters. The following combinations of electrode and VA
measurement mode are possible:
DC NP DP SqW AC CV PSA
DME (•) • • •
SMDE (•) • • •
HMDE • • • • • • •
RDE • • • • • • •
(•) This combination can only be used in the explo-
ratory mode.
The measured value pairs recorded per single measurement
sweep are stored in data blocks characterized by the VR number
(variation and replication). This identification can be used to se-
lect the single sweeps for display.