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SCAN-LAN Vt
3. Press INC (F3) or DEC (F2) to adjust the NVP value.
4. Press ENTER to save the new NVP value. A message indicates that the
new value has been entered.
5. Press ESC to exit the NVP calibration mode.
10.1.3 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 Vt. 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, usually between 50 and 90%. A default
NVP value is automatically set by the SCAN-LAN Vt based upon 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 will not impair
troubleshooting of a cable segment that used to work unless the length
measurement of a cable is close to the test limit (for example 100 meters on
a 10BASE-T segment).
When using the SCAN-LAN Vt for cable certification, determine the true
cable NVP and save the value. This will give you the most accurate cable-
length measurements and will avoid failing cable segments that are close to
the test limit.
10.2 Remote-Unit Calibration
Remote-unit calibration should be performed on a periodic basis in order to
maintain the accuracy of attenuation measurements. Remote calibration is
most sensitive to temperature changes. Allow both main and remote units to
stabilize to their operating environment before performing the calibration
procedure.
Each SCAN-LAN Vt is calibrated for remote operation at the factory. It’s
not necessary to re-calibrate the Remote unless a new SCAN-LAN Vt is used
