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CHAPTER 3: Getting Started
If the test does not pass, the remote unit displays:
3.1.2 NVP C
ALIBRATION
A typical NVP value will be automatically selected by the SCAN-LAN VI,
depending on the test standard that you choose. For greater measurement
accuracy, follow the NVP calibration procedure in
Chapter 10, Calibration
.
3.1.3 W
HY
D
O
I N
EED TO
S
ET
C
ABLE
NVP?
In order to make accurate cable-length measurements, the correct cable
Nominal Velocity of Propagation (NVP) value must be set in the SCAN-
LAN VI.
The NVP is a measure of how fast an electrical pulse travels down a cable
compared to the speed of light. NVP is expressed as a percentage and is
usually between 50 and 90%. A default NVP value is automatically set by
the SCAN-LAN VI based on the cable test standard selected.
Using the default value, however, may result in cable-length measurement
errors of up to 7%, due to the variation in the signal-propagation rate from
cable to cable. This potential length error usually won’t impair trouble-
shooting of a prior working cable segment unless the length measurement
of a cable is close to the test limit (for example 100 meters on a 10BASE-T
segment).
Summary of Contents for SCAN-LAN VI
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