ERICO EST401 ERITECH Clamp-on Ground Resistance Tester - Manual (Page 22)

20 www.erico.com
Field Applications
Above Telephone Space
Select the current range “A.” Clamp onto the ground wire and measure the current
(Fig. 23). The maximum current range is 30A. If the ground current exceeds 5A, resistance
measurements are not possible. Do not proceed further with the measurement. Remove
the clamp-on tester from the circuit, noting the location for attention, and continue to the
next test location.
After noting the current, select the ground
resistance range “Ω” and measure the resist-
ance directly. The reading you measure with
the EST401 indicates the bonding connections
between the Telephone ground and the Power
company ground. One of the following two
scenarios should be observed:
A. If “OL” or a high resistance reading
is displayed this would indicate no
bond has been established or a poor
connection exists between the
Telephone and Power grounds.
B. If and/or a very low reading is
displayed then the bond between
these two grounds has been verified.
General Measurement Notes
A reading of OL is most likely a cable that is not connected to the ground at both ends.
It may be there is no ground rod at all, or that there is no path back to the system neutral.
A reading which is < 0.1Ω generally indicates that the cable where you are clamped is
continuous with itself. You may have located a ground loop, which can usually be confirmed
by comparatively high current readings, also obtained when readings are taken at multiple
locations. A good low resistance ground may also have very high AC current flowing,
depending upon the type of equipment being grounded.
Figure 23
E1154IS06 EST401_5.qxd:E1154IS06 9/25/06 1:46 PM Page 20