Hello everyone, quick question about PI and DAR tests with a Megohmmeter. We’re testing a cable and getting 1.05/1.06 for both DAR and PI readings. Basically the 10min and 1min M-Ohm readings are so similar, that dividing them results in an answer of about 1. This is with two different brand IR testers used.
Does cable length need to come into play at all here? Our test cable is only about 20 feet long. So would you see higher DAR/PI numbers with a much longer cable? I understand the second number (10min reading) needs to be at least 1.5 - 2 times higher than the 1 minute reading for PI, then for DAR you’d want a higher number at 1 min vs 30 sec to get that proper reading.
Some more information about the cable size/type and test setup is needed. In general, shorter cables do not require very much charging current because they have lower capacitance. With only 20 feet, your insulation resistance value should stabilize fairly quick but still increase with time. Based on your readings, the insulation quality is poor/questionable. A “Good” DAR is considered 1.40 to 1.60 and a “Good” PI is in the 2.00 to 4.00 range.
