3660-MANUL-V01.01.00-CDC3 Operating Manual
Page 15 of 30
4.3.3
Cable Length & Sample Rate
The next field is for Cable Length. The units for this were set during the first run of the software. The Cable
Length field is not required, however if cable mapping is performed then an accurate cable length is of
great help.
Figure 26 shows the cable length and sample rate fields. When the cable length is blank, it is not possible to
alter the sample rate, and the sample rate will always be set to 40MHz.
Figure 26
Cable length and sample rate fields
The software attempts to select the best Sample Rate for the entered cable length. The sample rate is the
sampling interval used to capture the measured waveform. A higher sampling rate provides a better resolution
of the waveform being captured; however, this limits the maximum length of the cable that can be tested.
A lower sampling rate allows longer cables to be tested; however, the high-frequency resolution will be
reduced. If the cable length is an estimate, and the length is thought to be near to a length limit for the
sampling rate, it is recommended to choose a slower sampling rate to ensure that mapping is possible.
The theoretical maximum cable lengths for each sample rate are shown in Table 1.
Sample Rate
Maximum Cable Length (m)
Maximum Cable Length (Feet)
160MHz
2,800
9,186
80MHz
5,600
18,372
40MHz
11,200
36,745
Table 1 Theoretical Maximum cable lengths for each sample rate
Caution: If the cable being tested is longer than allowed by the selected sampling rate, then cable mapping will
not be possible from the data set. The maximum cable length is 11,200m. If this is exceeded, then the warning
message shown in Figure 27 will be displayed.
Figure 27
Warning when entering a cable length of over 11,200m