UMI Isolation Transformer AV-250 (250W) - Page 1
Forum section: electronics / testgear

author: dadler
author_rank: Unknown
timestamp: January 09, 2019, 04:08:21 pm
content: Any opinions on this isolation transformer?It seems intended for AV use (e.g. ground loop issues), but based on the specs it might be useful for low power isolation.https://smile.amazon.com/Isolation-Transformer-Conditioner-Shielding-AV-250/dp/B07595XJ3N/QuoteWill this device be effective as safety isolation transformer for working on low-power mains equipment?The form factor and industrial design make me want to pull the trigger, tear it down, share pics of the internal design with the forum, and hope it does what I want.Thanks for any opinions in advance,Dustin

author: dadler
author_rank: Unknown
timestamp: January 09, 2019, 05:46:53 pm
content: Well, I went and pulled the trigger anyways, couldn't resist.Amazon offered free same-day delivery so I may be able to post a teardown in the next few days.But feel free to comment on the product in the interim. If I like it, perhaps I'll return it for the 1000W model:https://smile.amazon.com/Isolation-Transformer-Conditioner-Shielding-AV-250/dp/B075983CQY/

author: nctnico
author_rank: Super Contributor
timestamp: January 09, 2019, 06:27:39 pm
content: Return it and buy a differential probe. Floating equipment isn't a good idea especially with an isolation transformer which isn't designed for that purpose in a lab which isn't built/designed for that purpose and finally operated by someone who isn't trained to measure in floating devices. A lot can go wrong!

author: 001
author_rank: Super Contributor
timestamp: January 10, 2019, 03:02:39 am
content: so silly diagramsince U=f(t) all ripples at sine wave must be vertical, not as shownI don`t trust this device

author: dadler
author_rank: Unknown
timestamp: January 10, 2019, 04:07:45 am
content: I have a differential probe, and an HP 54701A active probe as well.I was asking about this particular device, not the merits/risks of using an isolation transformer.I just wanted this device for a bit of extra safety+elimination of variables when something unexpected occurs. I want to use it with my rather simple circuits or defective equipment I am attempting to repair (say I want/need full galvanic isolation). For example, I intend my next significant project to be a low power, adjustable hybrid switch mode+linear power supply. I just want to potentially float what I am working on, perhaps just when powering the device on for the first time, not float say an oscilloscope unless absolutely necessary.And I am familiar with variacs/autotransformers and I understand the difference between these and isolation transformers. I want to use the isolation transformer+variac to (for example) produce low voltage AC that is not mains referenced, or use it to perform certain EMF/noise experiments/debugging. There are ways to work around these isolation transformer issues.Various EE videos (Dave, mikeselectricstuff, Mr. Carlson's Lab, Adafruit etc) convinced me to look into getting one, for hands on learning and just as a safety measure in certain circumstances. I may indeed have to modify the device to do what I want.I have one of these, and find it incredibly useful:https://www.amazon.com/gp/product/B015OA1J82/QuoteIt's floating and is powered by a 2-wire IEC-320-C7 with no direct earth reference.I am starting the design process to build a similar device that can also generate low-voltage/current AC as well. Just seemed like a good idea to have an isolation transformer around on my bench for when one is truly needed.It also looks cool and has two outputs, which means both connected devices would be at the same potential which has some utility.Did I mention it looks cool?Anyways, thanks for the response.And I am sure the eBay ad details/images are bullshit, but it will make a great teardown video! I like collecting test equipmentDustin

author: Gregg
author_rank: Super Contributor
timestamp: January 10, 2019, 04:46:49 am
content: I would return it and keep an eye on ebay for a medical grade isolation transformer preferably not made in China. For the same money I found a 600VA Toroid brand UL listed 120/240 to 120/240 volt true isolation transformer model ISB-060W. There are a couple of them on ebay presently.

author: dadler
author_rank: Unknown
timestamp: January 10, 2019, 06:12:22 am
content: I haven't tested it yet but I am almost certainly going to keep it due to the tiny form-factor. I'll keep a look out for a medical grade isolation transformer. Can't have too many toys!Externally, the build quality is excellent. I'll do the teardown later after I test that it works properly.Amazon same-day delivery came through:

author: dadler
author_rank: Unknown
timestamp: January 10, 2019, 06:58:44 am
content: Here is the product manual with some very rudimentary specs and info. <attached>Broken into many files due to attachment file size restrictions + frustration.