for detecting the strength of the electromagnetic field travels through the pipeline in a scraper or similar device senses the magnitude of the field and generates a signal indicative of the condition of the cathodic protection system application_number US 68916176 A description referring to fig1 pipe 11 and sacrificial anodes 12a and 12b are each disposed in a backfilled ditch 13 the two sacrificial anodes 12a and 12b ae rod like members placed in the ditch 13 on each side of the pipe 11 and oriented substantially parallel to pipe 11 it will be understood by those skilled in the art that multiple anodic members such as sacrificial anodes 12a and 12b are usually employed in installations in which pipe 11 is of large diameter to ensure that the entire surface of pipe 11 behaves as the cathode of a galvanic cell although this invention may be practiced in cathodic protection systems that employ a continuous anodic member electrically connected to pipe 11 at any number of points along the path of pipe 11 the invention can also be practiced in installations in which a plurality of separate anodic elements are disposed along the path of pipe 11 with each anodic element being electrically connected to the wall of pipe 11 the sacrificial anodes 12a and 12b are electrically connected to the pipe 11 by electrically insulated conductors 14a and 14b that are formed or wound in the shape of a solenoidal coil conductors 14a and 14b are electrically connected to sacrificial anodes 12a and 12b by conventional means for example connecting collar 16a securely fastens conductor 14a to.