In The design of a cathodic protection system it is necessary to predetermine the amount of current needed to protect the structure under consideration. This is usually arrived at by forced drainage of the structure, with a battery or generator, to a temporary ground bed and measuring the amount of current needed to satisfy whatever criteria are used to determine protection. It is desirous to interrupt this drain current at known periods in order to determine the change in structure potential as well as changes in neighboring structures.
Manual circuit interruption is tedious, inaccurate and requires manpower. A dependable automatic interrupter can be built by using the relaxation oscillator circuit shown in the sketch. Two tubes are used with resistance coupling, the output of one tube being fed to the input circuit of the other. The oscillation frequency is controlled by the reciprocating change of current through the charging and...
