Yes, it's important to recognize the limitations of a test method before relying on it. In this case, the A-B method was used at power frequency and below, to observe discharge time for UL testing. The MAIN advantage was not balance so much as that the chassis was isolated from the potential being measured by the impedance of its input amplifiers. This is an additional safety measure not provided by battery operation.
The _previous_ method used had been to remove the safety grounding terminal (pull the third pin) and float the whole 'scope at line voltage. The possibility of a mistake hooking things up made operators uneasy. An expedient to make channel gain difference less of a problem is to measure the point under test with both channels at once, in A-B mode, and as high a gain setting as possible without clipping in the input stage, then adjust their relative gains so that the offset on the screen is within a tolerable amount. This is often adequate for troubleshooting or specific tests. Cortland My thoughts alone are what I write Not my employers', on this night; I wish list members gathered here A happy, prosperous, New Year! ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
