Field Measurements 5:35
CP 1 – Cathodic Protection Tester Course Manual
© NACE International, 2000
02/01/05
Use of Current Interrupters
It is often desirable to determine the effect of a current source at various
remote locations. To accomplish this, a current interrupter is inserted in the
current source. An interrupter is a switch that is alternately turned on and
off on a regular timed cycle by some mechanical or electronic means. A
current interrupter is shown in Figure 5.19.
Figure 5.19 Current Interrupter
Coupon Measurements
Coupons are often used to check the effectiveness of cathodic protection.
These are made of the same metal as the structure and are electrically
connected to it. They are weighed prior to installation and then weighed
periodically to determine if any weight loss has occurred. Corrosion is
evidenced by weight loss.
Some test stations are equipped with a coupon so that structure-to-soil
measurements can be made with essentially no IR drop. Some of these test
stations have a stationary reference electrode built into them and some have
a nonmetallic tube from grade to the coupon which a reference electrode
can be lowered into.
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