-10-
V
．
Measuring Principle
1.
Voltage to ground measurement
utilizes
average value rectification
method.
2.
Earth resistance measurement
uses
fall-of-potential method. AC
constant current
I
is applied between the measurement object
E
earth
probe
and
C
(H)
current
probe
, and
calculating
the potential
difference
V
between
E
earth
probe
and
P
(S)
voltage
probe
,
calculating the earth ground
R
according to formula
R=V/I
. To ensure
test
method can eliminate
the
influence of contact resistance (usually
caused
dirty probes)
between measured earthing body, auxiliary earthing
probes
, test clips
and/or
meter’s input interface. The 4-wires method
can also eliminate influence of line resistance.
3
．
Maximum Operating Error
：
Operating error(B) is an error obtained
within the rated operating conditions, and calculated with the intrinsic
error(A), which is an error of the instrument used, and the error(E) due to
variations.
A
：
Intrinsic error
E2
：
Variation due to power supply voltage
E3
：
Variation due to
temperature change
E4
：
Variation due to interference voltage change
