Corrosion monitoring system using a metal pipe for transmission of

Abstract

In a monitoring system for protecting a metal pipe against corrosion, transmission of monitoring signals is carried out by the use of the pipe itself as a transmission line between a center station and a substation, which are coupled to the pipe at center and subordinate locations, respectively. The substation sends data signals over the pipe to the center station. These data signals represent the degree of corrosion that is measured at the subordinate location and are monitored by the center station. When a plurality of substations are coupled to the pipe, the center station selects a substation by transmitting through the pipe an address assigned to the substation. Each substation returns the assigned address to the center station in combination with the signals representing the measured degree of corrosion at the addressed substation. Preferably, the center station produces the selected address twice while each substation produces the assigned address and the measured corrosion signal, twice. Alternatively, the center station supplies a control signal in combination with the selected address, from the center station to remotely control each substation. A repeater may be interposed between the center station and the substation.