AEMC 6503 User Manual page 18

If the guard terminal is not connected at "B", the instrument mea-
sures the current "I" flowing through the insulation and a surface
leakage current "i1". See Figure 4-2.
To EARTH
terminal
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
16
Quality AEMC Products Online at:
A
I
A
I
GlobalTestSupply
www.
NO CONNECTION
to Guard terminal
B
i
1
Rx: resistance through insulation
Ry
Ry: surface resistance
Rz
Rz: surface resistance
Rx
To LINE
terminal
C
Figure 4-2
To Guard terminal
B
i
1
Rx: resistance through insulation
Ry
Ry: surface resistance
Rz
Rz: surface resistance
Rx
To LINE
terminal
C
Figure 4-3
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Megohmmeter Models 6501/6503
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