Specifications

Chapter 4 - Transient Protection of RS-422 and RS-485 Systems RS-422 And RS-485 Applications Ebook
Page 52 of 137 Manual Documentation Number: <DocNumber>
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IEEE C62.41 also specifies a 100 kHz "ring wave" test. The ring wave
has a 0.5 µs rise time and a decaying oscillation at 100 kHz with source
impedance of 12 ohms. Typical amplitudes for the 100 kHz ring wave
also range from 1 kV to 6 kV.
Figure 37: 100 kHz Ring Wave
Common Mode versus Differential Mode
Identifying the type of surges that may threaten a system is an
important part of selecting the appropriate levels and methods of
transient protection. Since each of the conductors in a data cable
travels through the same physical space, it is reasonable to expect
transients caused by environmental or current switching to be
"common mode" that is, present on all data and ground conductors
within the data cable.