tcgjr

AFAIK, stray current testing consists of measuring the potential (voltage) between two locations (typically 30-meters or 100-feet apart*) using a high impedance voltmeter or datalogger.

A fixed criteria of typically 50-mV is used to determine if there are possible damaging currents in the electrolyte.

• 1. Since only potential is being measured, how is current being tested?

Of course, current can be measured by knowing the resistance between the two locations. Therefore, it would be necessary to determine the resistance between the two locations to actually measure the current.

• 2. What is the basis for the 50-mV criterion?

* It would appear that the 30-meter spacing would be intended to reduce the resistance between the two locations to as close to zero ohms as possible. Thus, the 50-mV criterion would indicate that there is a substantial current present in the electrolyte. (0.050V/0.0000001Ω=500000A) Therefore, the test becomes sensitive.