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2 terminal + Guard connection example:
CAT III 600 V
G
G
g
- Figure 4
The GUARD lead (G) - refer to section 9 Insulation testing. is optional. When used it should be connected to the GUARD conductor,
screen, steel wire armoured conductor, or "user added" conductive wire or wrapper, such as foil. This "GUARD" conducts the
unwanted surface or "leakage current" away from the measured conductors.
7.3 3 terminal test lead connection
Three terminal connection provides measurement between the 3 pairs of a telecommunication cable (A-B, A-E & B-E) or between
single or three phase conductors (L-N, L-E, N-E) and (L1-L2, L1-L3 & L2-L3).
Alternatively, only a single pair can be used (default Red and Black) for conventional 2 wire measurement.
7.3.1 How 3 terminal connection works
The 3 terminal connections allow measurements to be made across any 3 terminals:
A-B, A-E or B-E (T-R, T-G, R-G)
This reduces the number of connections necessary to a circuit, especially where live working has been authorised. Once all three
leads are connected, measurements between the three terminals can be made.
For example:
Electrical testing:
Where two conductors need to be measured to a screen or shield
Where Live, Neutral and Earth need measuring
Comparing continuity of conductors to a ground terminal for difference measurements
Testing centre tapped electrical installations.
Telecommunications:
Testing voltage, continuity and Insulation between A, B and E or Tip Ring and Ground, without having to disconnect
test leads.
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