AEMC 3640 - 2-Point Measurement (Simplified Measurement)

Digital Ground Resistance Tester Model 3640 and 4610 31
4.7 2-Point Measurement (Simplified Measurement)
Thisisanalternativemethodtothree-pointmeasurementwhen an excel-
lent ground is already available.
Incongestedareaswherendingroomtodrivethetwoauxiliaryground
electrodesmay bea problem,the two-point measurementmethod may
beapplied.Thereadingobtainedwillbethatofthetwogroundsinseries.
Therefore,thewaterpipeorothergroundmustbeverylowinresistance
sothatitwillbenegligibleinthenalmeasurement.Theleadresistances
willalso bemeasured andshouldbe deductedfrom the nalmeasure-
ment.
Thismethodisnotasaccurateasthree-pointmethods(62%method),as
itisparticularlyaffectedbythedistancebetweenthetestedelectrodeand
thedeadgroundorwaterpipe.Thismethodshouldnotbeusedasastan-
dardprocedure,butratherasabackupintightareas.SeeFigure17.
Procedure:
• ShortXandXv(C1,P1)
• ShortYandZ(P2,C2)
• ConnectXtogroundrodtobemeasured
• ConnectZtoanelectrode
• Measureasinthethree-pointmethod
Ω
Press To
Measure
X-Z
Xv-Y
Xv-Y
ZYXX v
C1 P1 P2 C2
Fault
Hi Resistance
Hi Noise
GROUND RESISTANCE TESTER
MODEL 4610
AUTORANGING
REFER TO USER MANUAL
FOR FAULT WARNING LIGHT
EXPLANATIONS
!
®
INSTRUMENTS
25.4
Grounding conductor
Ground
level
Ground
rod
Butt plate
Utility
pole
Terminals shorted
Auxiliary rod
(Y-Z shorted)
Figure 17