Tektronix WFM 601i, User Manual

Page: 85 / 135

Measurement Applications
WFM 601i Serial Component Monitor
3–7
.7
.6
.8
.5
.4
.3
.2
.1
–.1
–.2
–.3
100%
50%
>100mV/DIV
OVERLAY
0.5nS/DIV
1 kHz
T
.8nS
Figure 3-6: Measuring 20–80% Risetime using cursors.
The WFM 601i Eye display has a –3 dB bandwidth of approximately 450 MHz.
This is a 20 – 80% risetime of 500 ps. This finite risetime must be considered
when determining the actual risetime of the source being measured. The actual
risetime of the source being measured can be calculated using the following
formula:
Ǹ
(T
R(measured)
)
2
–(0.5ns)
2
T
R(source)
=
T
R(source)
= the actual 20 – 80% risetime of the source (in ns);
T
R(measured)
= the 20 – 80% risetime measured on the WFM 601i (in ns)
Table 3–1 gives some conversion values between actual risetime and measured
risetime for the WFM 601i.