KYORITSU 4105A - Manual (Page 7)

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20 Ω when the earth resistance is low. This indicated value is the earth
resistance of the earthed equipment under test.
Note : If the auxiliary earth resistance of auxiliary earth spike C is too
high to make measurement, the display reads ' . . . '. Recheck the
connection of test leads and the earth resistance of auxiliary earth
spike.
CAUTION
If measurement is made with the probes twisted or in touch with each
other, the reading of the instrument may be affected by induction. When
connecting the probes, make sure that they are separated.
If earth resistance of auxiliary earth spikes is too large, it may result in
inaccurate measurement. Make sure to stick the auxiliary earth spike P
and C into the moist part of the earth carefully, and ensure sufficient
connections between the respective connections.
6-3 Simplified Measurement (with Test Probe M-7127)
Use this method when the auxiliary earth spike cannot be stuck. In this
method, an existing earth electrode with a low earth resistance, such as
a metal water pipe, a common earth of a commercial power supply and
an earth terminal of a building, can be used with two-terminal method
(E,P).
Use the simplified measurement probe attached which has a convenient
structure that both the safety alligator clip and the test bar are available.
q Wiring
Make connection as shown in the figure.
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6-2 Precise Measurement (with Test Probe M-7095)
q Test probe connection
Stick the auxiliary earth spikes P and C into the ground deeply. They
should be aligned at an interval of 5-10m from the earthed equipment
under test. Connect the green wire to the earthed equipment under
test, the yellow wire to the auxiliary earth spike P and the red wire to
the auxiliary earth spike C from terminals E, P and C of the instrument
in order.
Note : Make sure to stick the auxiliary earth spikes in the moist part of the
soil. Give enough water where the spikes have to be stuck into the
dry, stony or sandy part of the earth so that it may become moist.
In case of concrete, lay the auxiliary earth spike down and water it,
or put a wet dustcloth etc. on the spike when making measurement.
w Earth Voltage Measurement
Set the range switch to EARTH VOLTAGE position in the condition of
q . Earth voltage will be indicated on the display. Make sure that the
voltage is 10V or less.
When the display reads more than 10V, it may result in excessive
errors in earth resistance measurement. To avoid this, make
measurement after reducing the voltage by turning off the power
supply of the equipment under test etc.
e Precise Measurement
Set the range switch to 2000 Ω position and press the test button. LED
remains illuminated during testing. Turn the range switch to 200 Ω and