CLIOwin 6.5 PCI User's Manual - Audiomatica Srl

11.3 A BRIEF DESCRIPTION ON SETTINGS EFFECTS
11.3.1 STEPPED VS. NOT STEPPED
Although Measuring speed increases, use of a not stepped sweep can adversely affect
measuring results in several circumstances. As an example that should make clear also
other situation, let’s see what happens measuring the impedance of a woofer in Internal
or Constant Current Mode. Please refer to Measuring Impedance for more information
on this topic. In both conditions the loudspeaker is driven from a high impedance source
and its damping is only mechanical. Fig.11.1 shows a 6" woofer, driven by a 100Ohm
output impedance generator delivering a sinusoidal burst 200ms long, at its resonance
frequency. When the excitation stops, the device continues to move, and therefore
produce back electromotive force voltage for more than 50 ms. Something very similar
happens at start-up. In this situation, if CLIO is set in not stepped mode, it will acquire
the previously played frequency together with the actual.
0.200
CLIO
V
0.120
0.040
-0.040
-0.120
-0.200
0.00 50 100 150 200 250 300 350 400 ms 450 500
Figure 11.1
Fig.11.2 shows the same driver impedance taken both in stepped (black) and not
stepped mode (red). The not stepped curve is simply wrong. Conclusion: use always
stepped mode if the behaviour of the device to be measured is unknown.
25.0
CLIO
180.0
Ohm
Deg
20.0 108.0
15.0 36.0
10.0 -36.0
5.0 -108.0
0.0 -180.0
10 100 1k Hz
10k 20k
Figure 11.2
110 Chapter 11 - Sinusoidal