Metrohm 797 VA Computrace - Manual (Page 55)

3.2 VA measurement modes
797 VA Computrace – Software
43
Sweep parameters:
Hydrodynamic (measurement) [ on, off ; off ]
Enable/disable stirring of the RDE/SSE during the sweep.
Start potential (V) [ -5...+5 V ; -0.9 V ]
Start voltage for the voltage sweep.
End potential (V) [ -5...+5 V ; -0.1 V ]
Final voltage for the voltage sweep.
Voltage step (V) [ > 0 V ; 0.006 V ]
Voltage step for direct voltage ramp.
Amplitude (V) [ > 0...+1 V ; 0.02 V ]
Voltage amplitude of the square wave voltage superimposed
on the direct voltage.
Frequency (Hz) [ > 0...2000 Hz ; 50 Hz ]
Frequency of the superimposed square wave voltage, which
defines the voltage step time (
Voltage step time = 1 / Fre-
quency ).
Sweep rate (V/s) [ read only ]
Display of the ramp slope calculated as Voltage step × Fre-
quency .
Notes:
• The SqW measurement mode can only be used with HMDE or
RDE electrodes.
• If your curves have high noise, put Highest current range and
Lowest current range in the POTENTIOSTAT window on the
same level (see section 9.6 SqW Problems )
• The following condition applies to the definition of the
Voltage
step time :
Frequency ≤ 2000 Hz ⇒ Voltage step time ≥ 500 µs
• The measurement time
t (i) is defined as follows:
Voltage step time ≥ 80 ms → t (i) = 20/16.67 ms (power fre-
quency 50/60 Hz)
Voltage step time < 80 ms → t (i) = 0.5 × Voltage step time