BAS 100B/W Instruction Manual page 118

A.
RPM
Figure 10-28. Typical rotation rate (A) and potential wave form (B) for RDE.
Figure 10-29. Typical current response for RDE.
Hydrodynamic Modulation (HDM) is a related technique in which the frequency is
varied sinusoidally with time. More specifically, ω
to ω
1/2
. The A.C. current is handled using conventional data handling techniques; that
is, filtering followed by rectification or phase selective detection.
Consider the following example. According to the Levich equation, i
ω = ω + ∆ ω
1 2 / 1 2 / 1 2 /
sin
0
waveform of frequency
output is shown in Figure 10-31, and the processed I is shown in Figure 10-32. ∆i is
given by the equation
1 2 /
 
ω
∆i =
 
i
ω
ω
 
0
0
E
B.
FINAL
t
QUIET TIME
INIT
σ
t (ω is the base rotation rate that is modulated with a sine
o
= 2πf) and amplitude ∆ω
σ σ
(
10-50
1/2
is varied, since i is proportional
l
= Kω
l
1/2
(Figure 10-30)). The A.C.
t
1/2
, where