Corrosion monitoring system using a metal pipe for transmission of monitoring signals

A monitoring system for monitoring a degree of corrosion of a metal pipe surrounded by a mass, said degree increasing with time and varying from location to location along the length of said pipe, said pipe having a distribution of electrical potential along its length, the voltage levels of said potential distribution depending at least in part on said degree of corrosion, said system comprising:

• a center station coupled to said pipe at a predetermined location;
• and
• a substation coupled to said pipe at a preselected location and including means for detecting the degree of corrosion at said preselected location, means for supplying data signals to said pipe including a substation signal which is representative of the degree of corrosion detected at said substation;
• means at said center station responsive to the substation supplied data signals transmitted through said pipe to monitor the degree of corrosion detected at said substation;
• a plurality of said substations, each of said substations being identified by an individually associated address and being coupled to said pipe at prescribed locations, respectively;
• said center station comprising:
• selecting means for selecting said address numbers, one at a time;
• first signal producing means responsive to the selected address number for producing at least once a first address signal which is representative of the selected address number;
• and
• first signal supplying means coupled to said pipe and to said address producing means for supplying said first address signal to said pipe as a station identification signal;
• each substation comprising:
• measuring means coupled to said pipe for measuring the increase in the degree of corrosion at one of said prescribed locations to which said substation is coupled, to produce a resulting signal which is representative of the measured degree;
• holding means for holding a second address signal which is representative of the address number assigned to said each substation;
• second signal producing means responsive to the first address signal supplied through said pipe and responsive to said second address signal for producing a first energizing signal only upon coincidence of the address numbers represented by the supplied first address signal and said second address signal;
• and
• second signal supplying means responsive to said first energizing signal for supplying said pipe with said resulting signal as the substation signal of said substation.