Earth Resistance Measurement; Measurement Principle; P Recision Measurement (With Test Leads For Precision Measurement) - KYORITSU KEW4105DL Instruction Manual

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7．Earth resistance measurement
With the earth resistance measurement function of this instrument,
earth resistance of power distribution lines, in-house wiring system
and electrical appliances can be measured.
# DANGER
● B e extremely careful when measuring earth resistance; high
voltage, 50 V max is generated across H(C) ‒ E terminals.
● W hen measuring earth voltage, do not apply 300 V or higher
voltage between S(P) ‒ E and between H(C) ‒ E terminals.
● W hen measuring earth resistance, do not apply voltage, more
than 25 V, between measuring terminals.
7-1. Measurement principle
This instrument makes earth resistance measurement with fall-of-
potential method, which is a method to obtain earth resistance value
Rx by applying AC constant current I between the measurement
object E (earth electrode) and H(C) (current electrode), and finding out
the potential difference V between E and S(P) (potential electrode).
Constant current generator
～
Voltmeter
V
S(P)(Potential) H(C)(Current)
V = Rx × I
Rx = V / I
E(Earth)
7-2. Precision measurement (with test leads for precision measurement)
(1) Connection
S tick the auxiliary earth spikes S(P) and H(C) into the ground
deeply. They should be aligned at an interval of 5 - 10 m from
the earthed equipment under test. Connect the green wire to the
earthed equipment under test, the yellow wire to the auxiliary
earth spike S(P) and the red wire to auxiliary earth spike H(C)
from terminals E, S(P) and H(C) of the instrument in order. See
Fig. 7-2 and 7-3.
̶ 15 ̶
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15
10 20
5 25
0 30
I
Fig. 7-1
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