EEVblog Electronics Community Forum

Products => Test Equipment => Topic started by: dtryon on December 04, 2018, 12:56:19 pm

Title: AC Isolation Monitor
Post by: dtryon on December 04, 2018, 12:56:19 pm
Hey Folks,
I have tried to look but I can't find anything like I'm looking for. What I need is a circuit or kit or PC board design that will monitor AC line isolation. I need this to operate on a continuous basis. I want to monitor test equipment and or equipment under test so it remains isolated while being worked on. I would think someone has already designed something to do this function. I don't want to reinvent the wheel, lol.  :horse:  :-DD  Can anyone help me with this problem?

Thanks,
Dennis
Title: Re: AC Isolation Monitor
Post by: helius on December 04, 2018, 01:16:35 pm
An isolation test is "just" a resistance reading. Unfortunately, to test the resistance between two circuits requires a galvanic connection between them, which itself is not isolated. I don't think the monitoring device you envision is physically possible.
Title: Re: AC Isolation Monitor
Post by: 001 on December 04, 2018, 10:18:17 pm
Quote from: dtryon on December 04, 2018, 12:56:19 pm
Hey Folks,
I have tried to look but I can't find anything like I'm looking for. What I need is a circuit or kit or PC board design that will monitor AC line isolation. I need this to operate on a continuous basis. I want to monitor test equipment and or equipment under test so it remains isolated while being worked on. I would think someone has already designed something to do this function. I don't want to reinvent the wheel, lol.  :horse:  :-DD  Can anyone help me with this problem?

Thanks,
Dennis

 Supply Current = Load Current+ Leakage Current (if isolation is bad)
So Your bicycle is common leakage relay
Title: Re: AC Isolation Monitor
Post by: Neomys Sapiens on December 05, 2018, 12:44:31 am
Look here:
https://www.bender.de/en/know-how/technology/it-system/insulation-monitoring (https://www.bender.de/en/know-how/technology/it-system/insulation-monitoring)

Bender is the most original name for those, as they have pioneered this technology. They are represented directly or indirectly quite everywhere.

But other major electrical brands have their own versions. If the form factor (35mm rail and screw terminals mostly as usual in industrial applications) doesn't fit you, get the circuit boards out and modify them.
That is of course easier with the older models, the UI of which consisted of some LEDs, Pushbuttons/Switches and potentiometers/trimmers. Set the trimmers, replace annunciators and inceptors by optocouplers or whatever, and you can integrate the functionality discreetly into something.
Title: Re: AC Isolation Monitor
Post by: David Hess on December 05, 2018, 01:41:18 pm
Check out how the Tektronix A6901 Ground Isolation Monitor (http://w140.com/tekwiki/wiki/A6901) worked.