AMPP Cathodic Protection CP1 Certification Practice Exam - Practice Test & Study Guide

A multimeter reading of "OL" (which stands for "Over Limit" or "Open Loop") indicates that there is no continuity through the diode being tested. This typically occurs when the diode is open, meaning that it is not allowing current to pass through in either direction. In practical terms, an open diode behaves like a broken circuit, which is why the multimeter cannot detect any electrical connection.

When a diode is functioning properly and is forward-biased, it should show a specific voltage drop (typically between 0.6 to 0.7 volts for silicon diodes) during testing, resulting in a reading that is not "OL". Conversely, if the diode is reverse-biased, a multimeter will typically show a very high resistance but not necessarily an "OL" reading, as it can also indicate functioning but in the reverse direction. In contrast, a shorted diode would allow current to flow freely in both directions, resulting in a reading of zero resistance, which is also not represented by an "OL" reading. Thus, "OL" clearly indicates that the diode is open, confirming the correct response.