Multimeter Tests
Copper and G.fast/VDSL2/ADSL2+ Multi-play Test Set 139
Capacitance/Opens
Capacitance/Opens
The Capacitance/Opens test measures the electrical capacitance of the
loop and calculates length. Capacitive balance is also measured when all
pairs are selected.
Snapshot
The Capacitance/Opens test should be run with the far end open, as
electronics and equipment will skew or change the values. DSL splitters
also add some capacitance and change the values, as do some NIDs and
filtered wall plates.
The test gives you a quick indication of the length, to help you see if the
loop is too short and has an open. The capacitive balance is key and should
typically be 95 % (5 % imbalance) for POTS/internet, and better for high
speed broadband such as VDSL2. If the opens distance is significantly less
than indicated on plant maps, then the pair may be open at the distance
suggested. (Of course, if the distance matches the expected length, you are
seeing the end.)
Be a bit cautious with capacitance/opens, as wet faults or physical damage
can significantly change the result. Wetness can provide a path to ground
or other pairs which are then also included in the capacitance value and
not just the pair under test. Opens can usually be located using a TDR.
To access TDR from Multimeter tests:
1. Press
to return to the Copper Main menu.
2. Highlight TDR and press
to open the TDR menu.
3. Select either Auto TDR or Manual TDR to run the test. Auto TDR will
attempt to locate the nearest large event/reflection which may or may
not be the open.
TDR can also be run from Pair Detective.
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