The reading on the instrument measures what?

The reading on the instrument measures the structure to soil potential, which is a critical concept in understanding corrosion control on pipelines. This measurement indicates the electrical potential difference between the pipeline (structure) and the surrounding soil.

Understanding this potential is essential because it helps assess the likelihood of electrochemical corrosion occurring on the pipeline. If the potential difference is significant, it can indicate that the pipeline is either under cathodic protection or at risk for corrosion due to inadequate protection. This reading assists corrosion engineers in ensuring that adequate protective measures, such as cathodic protection systems, are in place to mitigate corrosion risks effectively.

Other readings such as current to load, strain on the pipe, or voltage drop do not directly convey the relationship between the pipeline and the soil, which is crucial for evaluating corrosion control strategies. Each of those alternative measurements serves different purposes within structural integrity assessments or electrical systems but does not focus on the direct environmental interaction impacting corrosion.