If the pointer fails to return to zero when...

Question 1 of 270705eccefa4bacbc34ba4d48423

If the pointer fails to return to zero when a hand-cranked megger is disconnected, what does this indicate?

Question 1 of 27070

If the pointer fails to return to zero when a hand-cranked megger is disconnected, what does this indicate?

🔍 Key Concepts

• Operation of a hand-cranked megger (insulation tester) and what the pointer should do when leads are open and the handle stops • How hair springs control the movement and return of the pointer in analog meters • Difference between a meter that is out of calibration vs. one that has a mechanical or internal fault

💭 Think About

• When you disconnect the megger and stop cranking, what electrical path should exist between the terminals? How much current should be flowing? • If the pointer does not come back to zero on its own, is that more likely caused by a scale/calibration issue or something affecting the pointer’s ability to move freely? • What is the role of the hair springs in returning the pointer to its rest position, and what would happen if they were damaged?

✅ Before You Answer

• Verify what the normal behavior of the megger pointer is with the test leads disconnected and the handle at rest • Consider whether out of calibration would change the zero point only slightly or prevent the pointer from returning altogether • Think about whether a mechanical sticking of the pointer looks different from a situation where the restoring force (like hair springs) is missing or damaged