I've yet to have a need for an isolation transformer at home. As for safety, I guess the only 100% sure safe way is pay someone who is competent to do the work.
I've yet to have a need for an isolation transformer at home. As for safety, I guess the only 100% sure safe way is pay someone who is competent to do the work.
I've occasionally wondered about getting one - and haven't found a use case. I have my bench powered through a simple domestic 30mA RCD.
If I wanted to invest money in protections, I'd go for a different RCD with a lower trip current. Mind you, that would probably pop every time I plugged in some old TE
Those who say "I have never found a need for an isolation transformer" have apparently not done much work on the hot side of SMPS devices!!! So much high power audio gear now have 'kilowatt plus' SMPS units for the + and - 100vdc and higher power rails and those SMPS's seem to be easily broken in cheaply made gear. You would be an idiot to probe around the hot side of a SMPS without connecting it through an isolation transformer. More than once I've seen idiots put the ground lead of a scope on a 'hot chassis' television where neither the scope or the T.V. was isolated. It didn't end well!!! Lots of smoke and a destroyed customer television!
Those who say "I have never found a need for an isolation transformer" have apparently not done much work on the hot side of SMPS devices!!! So much high power audio gear now have 'kilowatt plus' SMPS units for the + and - 100vdc and higher power rails and those SMPS's seem to be easily broken in cheaply made gear. You would be an idiot to probe around the hot side of a SMPS without connecting it through an isolation transformer. More than once I've seen idiots put the ground lead of a scope on a 'hot chassis' television where neither the scope or the T.V. was isolated. It didn't end well!!! Lots of smoke and a destroyed customer television!
I've yet to have a need for an isolation transformer at home. As for safety, I guess the only 100% sure safe way is pay someone who is competent to do the work.
Much of the troubleshooting with the SMPS could be done unpowered, using a Fluke 77, so it wasn't normally a major drama.
What about the idea of adding a second GFCI, and then not mounting it in the regular way, but only hook up the earth wire though the sense circuit. That way, whenever there is a current though the earth wire, it will turn off your desk and all equipment on it.
What about the idea of adding a second GFCI, and then not mounting it in the regular way, but only hook up the earth wire though the sense circuit. That way, whenever there is a current though the earth wire, it will turn off your desk and all equipment on it.
I see two major issues. No power supply for the sense circuit (usually some special RCD/GFCI IC). And the built-in test function won't work.
Coppercone mentions blowing up $200K scopes as trivial? We are in an era now where differential probes are selling for $5K plus and the last scope we bought for differential logic measurements in the 2GHz+ range was $400K. Blowing them up is not trivial if you expect to remain in business. They are often damaged beyond repair when damage occurs. But, sadly, where I was working there was very little inspection of test setups by senior engineers prior to the circuit being energized and we had some degree'd H1B engineers running the testing whom I swear got their degrees from a Cracker Jack box and that is because the company hired 'degrees' and not proven talent!! I have seen a lot of gear get destroyed by idiots who I would have guessed knew better. We have one person who claims to have been a professor and that person was responsible for a lot of damage. They seemed clueless about the very job they were hired to do! I walked in a couple of times and immediately hit the master lab kill switch just glancing at their testing methods!! They had not a clue what 1700uf charged to 1400vdc could do to them! everything exposed, nothing isolated!!
They were trying to determine the actual capacity at 1400vdc. They were going to measure the voltage decay time across a 1K 1 watt resistor to determine total uF capacitance! Glad I walked in!! May have saved a life!! Some of the 'Senior Engineers' were 40 years my junior with no more experience than a college degree. When I would point out flaws in their methods the reply was always "You're old school man".
Yay! Another isolation transformer bashing thread. The actual problem is to understand how to use an isolation transformer properly and when to use one. GFCIs/RCDs also come with a few issues, e.g. different trigger types, regular testing, or trigger currents (30mA can kill you). No matter if it's an isolation transformer or a GFCI/RCD, you can do stupid things with both of them and harm yourself. And please don't rely on just a single safety measure!
Isolation transformers can provide a degree of safety when working with high voltage equipment (device under test or DUT). Here, I’m defining high voltage as a voltage as one that can give a harmful shock via dry skin contact. However, the safety provided by isolation transformers can be easily defeated. Worse, isolation transformers can nullify the benefits of better protection … a GFCI/RCD-protected power source.
Now, all you have to do to get shocked is touch two hands to high voltage parts of a DUT.
Much of the troubleshooting with the SMPS could be done unpowered, using a Fluke 77, so it wasn't normally a major drama.
That has been my experience.
They don't allow you to randomly fondle, grope and poke your DUT with your sweaty fingers nor ...
There is absolutely nothing special about that scope, as far as I can tell, in comparison to any other low / mid range scope in the market today, apart that it can use a battery.
Exposed metal back and front referenced to the ground of the BNCs.
Somehow it´s ok to float that scope and not others. Again, I do get that most isolation transformers are leaky and that might be a concern.
The TDS3000 series is 100% absolutely not intended to be used floating.
Scroll down further on the same page for an example in the THS700 -- an oscilloscope built from the ground up for isolation.
The TDS3000 series is 100% absolutely not intended to be used floating.
Scroll down further on the same page for an example in the THS700 -- an oscilloscope built from the ground up for isolation.
Actually they say you can use it floating if you are "sure" that the circuit you are testing has no voltages greater than 30VRMS to ground. The channel grounds are all common, of course.
I don't know when that document was published, but they don't mention the TPS2000 series which is the only Tek lunchbox-style scope that is actually properly isolated both from ground and between all channels.
It does not indicate that you can float the instrument.