AEMC 6503 - Page 18

16 MegohmmeterModels6501/6503
Iftheguardterminalisnotconnectedat“B”,theinstrumentmea-
sures the current “I” owing through the insulation and a surface
leakagecurrent“i1”.SeeFigure4-2.
To EARTH
terminal
I
To LINE
terminal
NO CONNECTION
to Guard terminal
A
B
C
Ry
Rx
Rz
Rx: resistance through insulation
Ry: surface resistance
Rz: surface resistance
i
1
Figure 4-2
Whentheguardterminalisconnectedat“B”,theinstrumentmea-
suresthecurrent“I”andnotthesurfaceleakagecurrent“i1”,which
is not included in the measurement. See Figure 4-3.This type of
measurementwillgivethetruevalueoftheresistance“Rx”,provid-
ingthe“Ry”and“Rz”arenottoolow.
To EARTH
terminal
I
To LINE
terminal
To Guard terminal
A
B
C
Ry
Rx
Rz
Rx: resistance through insulation
Ry: surface resistance
Rz: surface resistance
i
1
Figure 4-3
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