JANUARY 31 2003
IMPRESSED CURRENT ANODE BED. The impressed current anode bed
survey is a non-interrupted survey of the ground bed to determine the condition of the
anodes. It should be comprehensive and thorough to identify any possible problem with
the impressed current anodes. It may also be used to predict failure and to program
replacement. This survey would normally be done together with the close-interval
As a minimum, an impressed current anode bed survey should include ON
potential over-the-anodes at intervals described in Table 4-7, unless the system has
incorporated other means for monitoring the anodes (e.g., individual anode leads in an
anode junction box).
Table 4-7. Recommended Over-the-Anode Intervals for the Impressed Current
Anode Bed Survey
CP SYSTEM TYPE
Measure anode-to-soil potentials at 0.6-meter
(2-foot) intervals along the length of the anode bed, beginning 3
meters (10 feet) before the first anode, and ending 3 meters
past the last anode in the ground bed.
Plot test results on graph paper to give a visual
indication of the anode bed condition.
Measure one anode-to-soil potential with the reference cell
located directly over each anode.
In lieu of anode potential measurements,
measure anode circuit current using (in order of preference)
a clamp-on milliammeter, a multimeter measuring millivolts
across a calibrated shunt, or a multimeter connected in
series measuring milliamperes.
Measure the anode current for each anode if
separate leads are available.
IMPRESSED CURRENT SYSTEM CHECK. The impressed current system
check is an operational check of the impressed current system to ensure the system is