Viavi OneExpert DSL User Manual page 92

Chapter 4 Copper Testing
- Press the OK button.
4. To specify the method to test opens/capacitance, press the Tray button, select Opens
Method, and then choose 2-terminal, 3-terminal, Enhanced 2-terminal, or
Enhanced 3-terminal.
The three terminal is the default Opens mode that measures the capacitance across the
pair or from an earth reference to either wire in the pair using only two connections or
terminals
The three terminal method measures the capacitance across the pair in the same way
except the way it measures from an earth reference to either wire in the pair. Connect
all the other unused pairs, screen (shield) if any, and ground or earth to the unused (not
being tested) wire in the pair, using three terminals.
Three terminal mode is useful when testing a pair inside a multi-pair cable since all pairs
rotate or change their relative position inside the cable throughout the length of the
cable to help control crosstalk.
The enhanced terminal modes are specially designed to perform better in low-parallel or
high-series resistance environments, where normal opens meters have difficulty getting
accurate results. After selecting an enhanced mode, simply return to the measurement,
and test as you normally would. You will get more accurate results in resistive
environments.
NOTE:
When using the three terminal method and no earth terminal
is connected, you will get a non-zero result from each wire to
earth.
5. For greatest accuracy, VIAVI recommends that you compensate the opens measurement
to remove the effects of the test leads. To compensate the opens measurements:
Swipe downward on the screen to access the Tray menu.
y
Select the Compensate OPENS system key
y
Follow the instructions on the screen to disconnect all test leads to perform test
y
lead compensation.
Press Compensate.
y
6. Press the Back button to return to the Opens menu.
92
μF/mile (or other units depending on your configuration).This value is used
for capacitance between Tip (A) to Ground (E), and Ring (B) to Ground (E).
The compensation stops automatically when finished.
OneExpert DSL User's Guide
22052280, Rev. 016 May 2020