To isolate the output receptacle grounds you could replace the black internally strapped receptacles with isolated ground hospital grade receptacles (orange color with green dot and green triangle). This way you do not need a cheater plug. You could also have an isolated floating plate to mount the receptacles to but this would be more work.
You probably saved my Oscilloscope from blowing up. Did not realize the mounting screws and grounding hole were connected. I am now going to order the Isolated ground receptacles from Ebay, referenced a few comments down. Thanks much!
I learn this the hard way, I blew up one of my Oscilloscope and Had to do some intensive repairs. I have an Isolation transformer now which I modify to use the 3 prong plug. What I did was use an isolation between the transformer and the chassis case, so the ground from the mains are connected to the transformer base but not the chassis.
Couldn't you have allowed the chassis of the transformer to still be grounded and just prevented the earth ground from being connected to the ground pin of the IT's outlets? Or was that too much modification? I swapped out one of my IT outlets with an isolated ground receptacle so that it was not grounded to the chassis. I left the other set of original outlets grounded to the chassis. Mine are labeled so that I can just choose whichever set meets my current needs.
Hi Derick, yes it I could of done that but my base is made out of wood which the transformers are mounted and that is why I grounded the transformer case.
Never remove the ground from your test equipment. Isolate you equipment that your testing. Also use a current limit high wattage light bulb in AC circuit. Use caution Always!!
Some isolation transformers are balanced to filter noise. They balance it by putting a center-tap on the secondary which is grounded. Needs to be disconnected
Hi- can I use a variac with isolated transformer , to protect my scope and signal generator and others instruments. Also can put a power bar in isolated Variac out put transformer so that I float the grounding on my test instrument and circuit under test ? let me know ----- thank you , Jerry
No!. Never float test equipment. Only float DUT (device under test). You can obviously use a bar strip on the output but why would you? You’re only testing one DUT at a time.
I bought a new isolation transformer for my 14 year old future electrical engineer. I am wondering why I bought it! Perhaps because I have seen so many TH-cam videos on I/T’s. Such a gadget will not prevent electrocution when working on 240 vac projects. It will only protect the scope and other equipment. I use a RCD (residual current device) also referred to as a (DCD, differential current device on all my circuits, in fact 22 of them. In Australia we have 240 vac and the common ground (neutral) is tied to the ground stake as a safety measure, same as in many other countries. If I am working on any 240 vac equipment and I for some reason touch the active wire, the power goes off within 30 m/s when a differential of 15 mA is detected. So the scope is off and I am safe. Why do I need an I/T ? I am going to test this out on my own equipment by shorting something out when connected to the scope. I paid $250 for the I/T. The RCD’s cost about $15. I see someone suggested a $400 device on the probe to protect the scope, yes, but that doesn’t protect your life. I am not getting it, can someone please explain to me why a $15 gadget will not only protect the scope and my life?
I’m still so confused! I’ve read many books, and watched many TH-cam videos about floating grounds. What I want to know is, when working on a “Hot Chassis” old tube amp, what should I do to get the ground off of the HOT side of mains? If I don’t get rid of ground, wouldn’t I be blowing up my scope?
If you connect the hot chassis radio t the transformer as you should then it does not really matter what there is in the ground contact as it is not used.
Use the isolation transforer to isolate the radio (or whatever). This way, when you ground the scope to item under test, it's not hot in relation to ground. Some of us old techs float our scopes because back when we worked on main frames where many of our calibrations required both the scope probe and ground were both elevated above ground. For decades, I used scopes with defeated grounding. I never even have to consciencly think about it any more, I just know it's floating. However, I do not recommend a beginner to do this.
Yes, very useful for people that know what they are doing, very dangerous for those that don't. The rule is simple with grounding, don't fool around with it unless you are 110% sure you know what you are doing.
This ST 1500W powering my guitar amp. DVM Continuity test shows mains neutral across all recepticals, that have no ground so it's ground isolated; but neutral not so much. Is that any good for an isolation transformer or should I open and remove the neutral cross comnects to all ouyputs?
Yes you could do that (and is often done), and it is a good solution to protect your device and yourself. But be aware of the possibility of ground-loops (Google for this).
In arcade monitors which need an isolation transformer in most cases have earth ground connected to the chassis ground on the monitor. I don't understand how this is safe.
thank for the great vid - Do we usually power the SYSTEM UNDER TEST using the ISOLATION Transformer, & the AC TEST EQUIPMENT/oscilloscope is powered as usual via residential AC outlet ? OR BOTH SYSTEM UNDER TEST and AC TEST EQUIPMENT/oscilloscope is powered via ISOLATION TRANSFORMER ?
I never ever float any test equipment. Only my device under test. You will forget someday that a piece of test equipment is floating and damage it or yourself not realizing it is not grounded.. When floating the device under test caution should always be taken because noting is ever a sure thing. One wrong hookup can lite something or you up.
I re-reviewed your video to get a refresher on the topic - yours is one of the easiest to understand out there - thank you for that. On to my question: So in a nutshell, for a TECH isolation transformer setup, when using a DUT (device under test) with 3-prong AC plug : Is the reason you want to eliminate the EARTH/GROUND on the secondary side outlet (where the DUT is connected) with the methods you stated, lifted adapter.... - because then you can safely connect the SCOPE EARTH CLIP to ANY part of the DUT (such as the chassis itself or even any of the 2 secondary windings L or other L as per your diagram etc). In which case, the accompanying SCOPE PROBE TIP can safely measure the potential difference (observe voltage) between the probe tip point and earth clip point? (and this in effect is much safer when measuring this way) OTHERWISE if there was indeed an EARTH/GROUND on the secondary side outlet extending to the DUT, then in the case where the SCOPE EARTH CLIP is accidentally connected to a point on the DUT which is at line voltage L (120VAC, same as either of the secondary windings for example, then this situation will cause a short and blow the scope and may even cause personal injury/harm etc ,In this case, the ONLY real safe point to clip the EARTH SCOPE CLIP is any point on the DUT that is indeed at EARTH GROUND potential - but because on a device being tested for repair, that fact may not necessarily be the case hence why it is safer to eliminate the GROUND EARTH path from the DUT.... Would you say the above is accurate summary for your video? I can see why you stated it is important to understand CLEARLY everything involved, before diving into this stuff...I am looking forward to your reply. Please correct me as necessary.. i want to thank you again - your video has helped me understand better the topic. God bless!
I suppose you could as long as you understand the case is now floating and anything that is plugged in that has a third pin ground is now going to put the isolator case at that potential. Of course any type of isolation transformer for tech use is not fool proof. Cation is always needed. You could get a shock regardless of isolation depending on the unique configuration.
Grounding the outlets via the screws seems like a gotcha. Guess it is always best to check for (lack of) continuity between output grounds and electrical plug ground pin or just bypass the grounds entirely by using a cheater plug.
Works fine. It has a slight hum but it is not bad. All big linear transformers hum. Don't forget the ground passes through if you are using it for tech use..
@@joebiz22 You may be interested to know that the steel laminations in the transformer actually change length due to the magnetic flux. It's called magnetostriction and it happens 100 or 120 times per second depending on whether you have a 50 Hz or 60 Hz supply, so that is why all power transformers will hum.
New Subscriber - I have been looking for this video for some time. Thanks so much! Bought my used scope, but have been afraid to use it on AC items after discovering this grounding issue. Also, some long time techs (12voltvids and others), tell you to float both the scope and project. So, quick questions... Scope Earthed, Project Floating - Once you connect the ground lead from CH1 to a chassis (all channels on that scope are on the same ground), the problem is that the voltage could be different where each probe is connected (Ch1 vs CH2 potential). Is that right? Scope Earthed, Project Earthed (To Same House Panel Ground) - It's the same ground, so why is this an issue? I made a "dim bulb" system to use, but screwing with varying wattages is a hassle. Another story for another time. I'm missing something still. Thx!
First answer- Once you hook up the ground on the scope to an isolated project then all scope channels will have to be attached to the same point. Unless the scope has isolated channels, which most don't. Second answer. You can, If both are grounded then you can use the scope on the device but you have to hook up the channels from the scope to a ground on the device, "NO" where else or BOOM.
Can I use an isolation transformer to power a modified atx bench power supply, for safe use with an oscilloscope in circuits powered by the atx supply.
I wouldn't see why not. As long as it can be isolated. I would test to make sure when it is hooked up use a multi meter and start probing potential concerns. The grounds might be the biggest issue. Always use caution when working with underground equipment and isolators. It is not code to default your grounds but in a tech modified isolater the game changes and you have to know what your actually doing to not get hurt.
Thanks for an excellent explanation. My question: and I forgot to mention that in the USA, the safety device is called GFCI and in Australia a RCD, same thing.... so my question is: if I have a GFCI outlet supplying power to my scope as well as to the mains board I am working on,,, two separate connection but from the same GFCI outlet. Whatever I mock up on the work piece wrongly will trip the GFCI,,,,, so why do I need an I/S which only will save the scope but not my life???? I must be wrong, because everywhere I see that you need an I/T... Please help.
bro i have also been thinking about the same thing... if my test piece is being powered by Isolation trasnformer, now if I mess up on something instead of tripping the gfci its going to elelctrocute me because its isolated from the main breaker board ... I am also concerned about this...
Hint #1: if you don’t need ground pin your receptacle, go to home bipot, - and by that receptacle, witch has no ground slots on it!!! That’s how you can be 1000000000000000000% isolated from main ground! Hint #2: if you need that pin on your receptacle, go to home depot and by that hospital rated receptacle (orange color: with green dot, or triangle) That’s how you can be 1000000000000000000% isolating from main ground!
The easy way to modify it is to replace the RECEPTACLES with ISOLATED GROUND DUPLEX RECEPTACLE PLUG OUTLET 120V 15A 20A AMP ORANGE. you can get them from ebay for about $6. The the ground hole is not connected to the mounting screws.
David Geltz That’s a BAD idea. That will just float the ground on whatever you plug into it. Do NOT flat your scope. So if you plug your scope into an outlet like this, that’s NOT good. It can NOT separate the ground tied to the neutral in the main breaker box, so you still have a path back to ground and will be electrocuted if you use this in the US. Your still at risk for injury or death. Maybe this is why it says 50Htz in the ebay ad since other counties are wired differently. Still not a good idea on a main 50Htz to use something like this, and if you have to buy an outlet for this the you don’t know enough to about mains or AC voltage and shouldn’t be testing with it. The older medical grade isolation transformers like his floats the device under test, not the testing equipment. Still not 100% safe and you can still make a mistake wiring something or using two probes but it’s safer then floating your scope. Your best best if you don’t understand his video is buy a battery operated oscilloscope.
@@GadgetReviewVideos I think you're confused. He's not talking about floating the scope. He is talking about using a 3 prong plug from the DUT to the output of the isolation transformer replacing the existing outlet with one that has the 3rd ground hole but is not connected to earth ground.
This is getting confusing. There are many videos out there that say to isolate the oscilloscope and now this video says not to do that. Sounds like two different doctors prescribing different meds for the same condition. it sounds like you can blow up your scope no matter what step you take.
50 ears ago wen i become electrician and T.V epairman no ground back then on a devices or plugs but some radios ,,,and no so,,,,have 2 grounds on a shematic ( chassis ground and power supply ground ) the scope was rock up on chassis and when you want tack a dc voltage measure the ground clip go on - side of power supply , today a toilet cleaner work on electronics, BAD, VARY BAD
Doesn't anybody use differential mode any more? That way no earths are used. One channel becomes the "virtual" earth. You disconnect the earth leads from the scope probes.
Hold on a sec... If the oscilloscope is floating, then there is no path to ground so it does not matter if it's frame is at high voltage ...the issue happens when you touch both sides of the power source. ....so, it's the same issue....never bridge things with your body! Period
Thankyou for your explanation! This question is 100 % sincere and NOT confrontational!!! Why? Do You Very expert, type of guys , who obviously go to great extents, to set up great work benches, simply, go out side your home, sink an eight foot REBAR ROD into the ground, Hook a good cable to it, and pass that cable which is an INDEPENDANT EARTH GROUND STRICTLY FOR SAFETY BACKUP PERPOSES, TO YOUR WORK BENCH, WHICH CAN SERVE AS A INDEPENDANT EARTH GROUND, STRICTLY FOR BENCH TESTING-----WHICH IS 100 % ISOLATED FROM THE HOUSE MAINS NEUTRAL GOUND CIRQUIT, AS WELL AS THE EARTH GROUND CIRQUIT WHICH IS CONNECTED TO THE PLUMBING SYSTEM AS WELL; WHICH IS ACTUAL EARTH GROUND AS WELL; BUT IS PART OF THE MAINS AC POWER SYSTEM, AS THAT SYSTEM IS ORIGINALLY WIRED INSIDE THE MAIN POWER PANEL OF THE BUILDING? This way, you would have an isolated path to earth gound for testing, which is completely "Floating" as you termed it, from the main ac system of the building! ?????? What is wrong with that??? Too Much trouble??? Thankyou ! kennethzakaib607@gmail.com (AND A BIG CHICKEN THAT DOES NOT WANT TO GET BBQ-ED !!! ) THANKS!
Driving a ground into earth is not going to isolate you much. Depending on the nearest electrical grounding point and soil conditions it could conduct with the order of some resistance. Device under test using a isolation transformer and grounding test equipment is good enough if you know what your doing.
We took a vote. Go back to your "multimillion dollar designs." When you figure out why it's a bad idea to bond one leg of the secondary to the Neutral, Ground and Equipment Grounding Conductor of the primary on an isolation transformer, let me know.
That's great go ahead and float your scope. Please explain how floating a scope is much safer. They both have their caveats. The way I do i and most other techs do it the way I explained for a much less chance of self and equipment harm. Pleas do yourself a favor and tally up all the tech videos just here on TH-cam of people floating their scope vs floating the device under test. Here is a question right out of an EE test website. Question No. 1:You have to troubleshoot (with an oscilloscope) a piece of equipment that is mains powered and has test points at or near mains live potential. You have an isolation transformer at your disposal. Which should thed the isolation transformer power? A The oscilloscope B The equipment under test C Both of them. The correct answer is b, the equipment under test -- that will prevent it being at mains potential with respect to earth, which could be very dangerous. Can you let it go and admit you are just plain outright wrong.
You have deleted most our comments on this subject because you are removing all my valid arguments why you are wrong. There was many many valid arguments. If you felt you were correct you would have left everything as it was in the comments to let everyone else chime in. But since I have secretly got through, you felt silly being a teacher and acting so childish when proved incorrect in the practice of the use of a "tech modified" medical isolation transformer for DUT.
Kev31779 this is why I get email notifications of comments, it gives me proof and a record of the comment they deleted, then I can copy/paste it back into the comment thread. In this comment, I wold just delete the whole comment.
To isolate the output receptacle grounds you could replace the black internally strapped receptacles with isolated ground hospital grade receptacles (orange color with green dot and green triangle). This way you do not need a cheater plug. You could also have an isolated floating plate to mount the receptacles to but this would be more work.
Thank you. You may have averted a catastrophe for me. I was thinking about floating my oscilloscope. Good thing I searched "what if".
You probably saved my Oscilloscope from blowing up. Did not realize the mounting screws and grounding hole were connected. I am now going to order the Isolated ground receptacles from Ebay, referenced a few comments down. Thanks much!
I've been watching many videos on this subject, and it has finally made sense and clicked. Thanks for your video!
No problem. Glad it helped someone. It can be a bit tricky to understand the concept.
Thanks for the help in keeping me alive. My ex-wife wouldn't like you for it..........HaaaaaHaaaaa
NOW I understand.
I learn this the hard way, I blew up one of my Oscilloscope and Had to do some intensive repairs. I have an Isolation transformer now which I modify to use the 3 prong plug. What I did was use an isolation between the transformer and the chassis case, so the ground from the mains are connected to the transformer base but not the chassis.
Couldn't you have allowed the chassis of the transformer to still be grounded and just prevented the earth ground from being connected to the ground pin of the IT's outlets? Or was that too much modification? I swapped out one of my IT outlets with an isolated ground receptacle so that it was not grounded to the chassis. I left the other set of original outlets grounded to the chassis. Mine are labeled so that I can just choose whichever set meets my current needs.
Hi Derick, yes it I could of done that but my base is made out of wood which the transformers are mounted and that is why I grounded the transformer case.
After about an hour of searching I found your video, which answered my exact question. Thanks.
Never remove the ground from your test equipment. Isolate you equipment that your testing. Also use a current limit high wattage light bulb in AC circuit. Use caution Always!!
Great video! Thanks.
Some isolation transformers are balanced to filter noise. They balance it by putting a center-tap on the secondary which is grounded. Needs to be disconnected
I luv your vids ,I learn so dam much and ur a nice guy that explains yourself...keep up the good work..always 👍
Thanks for the kind words.
Kev31779 thank you for sharing your knowledge...
Hi- can I use a variac with isolated transformer , to protect my scope and signal generator and others instruments. Also can put a power bar in isolated Variac out put transformer so that I float the grounding on my test instrument and circuit under test ? let me know ----- thank you , Jerry
No!. Never float test equipment. Only float DUT (device under test). You can obviously use a bar strip on the output but why would you? You’re only testing one DUT at a time.
Super Video, thanks ...
I bought a new isolation transformer for my 14 year old future electrical engineer. I am wondering why I bought it! Perhaps because I have seen so many TH-cam videos on I/T’s. Such a gadget will not prevent electrocution when working on 240 vac projects. It will only protect the scope and other equipment. I use a RCD (residual current device) also referred to as a (DCD, differential current device on all my circuits, in fact 22 of them. In Australia we have 240 vac and the common ground (neutral) is tied to the ground stake as a safety measure, same as in many other countries. If I am working on any 240 vac equipment and I for some reason touch the active wire, the power goes off within 30 m/s when a differential of 15 mA is detected. So the scope is off and I am safe. Why do I need an I/T ? I am going to test this out on my own equipment by shorting something out when connected to the scope. I paid $250 for the I/T. The RCD’s cost about $15. I see someone suggested a $400 device on the probe to protect the scope, yes, but that doesn’t protect your life. I am not getting it, can someone please explain to me why a $15 gadget will not only protect the scope and my life?
I’m still so confused!
I’ve read many books, and watched many TH-cam videos about floating grounds.
What I want to know is, when working on a “Hot Chassis” old tube amp, what should I do to get the ground off of the HOT side of mains?
If I don’t get rid of ground, wouldn’t I be blowing up my scope?
That is why you use a isolation transformer modified for tech use to power the device under test.
If you connect the hot chassis radio t the transformer as you should then it does not really matter what there is in the ground contact as it is not used.
Use the isolation transforer to isolate the radio (or whatever). This way, when you ground the scope to item under test, it's not hot in relation to ground.
Some of us old techs float our scopes because back when we worked on main frames where many of our calibrations required both the scope probe and ground were both elevated above ground. For decades, I used scopes with defeated grounding. I never even have to consciencly think about it any more, I just know it's floating. However, I do not recommend a beginner to do this.
Yes, very useful for people that know what they are doing, very dangerous for those that don't. The rule is simple with grounding, don't fool around with it unless you are 110% sure you know what you are doing.
This ST 1500W powering my guitar amp. DVM Continuity test shows mains neutral across all recepticals, that have no ground so it's ground isolated; but neutral not so much. Is that any good for an isolation transformer or should I open and remove the neutral cross comnects to all ouyputs?
Can I run a ground rod separate from my house ground connection and be completely isolated from my home wall supply?
Yes you could do that (and is often done), and it is a good solution to protect your device and yourself. But be aware of the possibility of ground-loops (Google for this).
Hi.. which one would you recomend to surge protection?
In arcade monitors which need an isolation transformer in most cases have earth ground connected to the chassis ground on the monitor. I don't understand how this is safe.
I still don't understand why does it have a 3 prong plug? I have an old isolation transformer and it has a 2 prong plug but the new ones have 3 ?
New ones are grounded and have to adhere to safety standards. These are not for tech use out of the box.
thx for the ans. and some good explanations.
Wouldn't I want to connect my alligator clips to the earth grounded chassis of the device being tested?
thank for the great vid - Do we usually power the SYSTEM UNDER TEST using the ISOLATION Transformer,
& the AC TEST EQUIPMENT/oscilloscope is powered as usual via residential AC outlet ?
OR
BOTH SYSTEM UNDER TEST and AC TEST EQUIPMENT/oscilloscope is powered via ISOLATION TRANSFORMER ?
I never ever float any test equipment. Only my device under test. You will forget someday that a piece of test equipment is floating and damage it or yourself not realizing it is not grounded.. When floating the device under test caution should always be taken because noting is ever a sure thing. One wrong hookup can lite something or you up.
@@The_Active_Region the for the guideline.
I re-reviewed your video to get a refresher on the topic - yours is one of the easiest to understand out there - thank you for that. On to my question:
So in a nutshell, for a TECH isolation transformer setup, when using a DUT (device under test) with 3-prong AC plug :
Is the reason you want to eliminate the EARTH/GROUND on the secondary side outlet (where the DUT is connected) with the methods you stated, lifted adapter....
- because then you can safely connect the SCOPE EARTH CLIP to ANY part of the DUT (such as the chassis itself or even any of the 2 secondary windings L or other L as per your diagram etc). In which case, the accompanying SCOPE PROBE TIP can safely measure the potential difference (observe voltage) between the probe tip point and earth clip point? (and this in effect is much safer when measuring this way)
OTHERWISE
if there was indeed an EARTH/GROUND on the secondary side outlet extending to the DUT, then in the case where the SCOPE EARTH CLIP is accidentally connected to a point on the DUT which is at line voltage L (120VAC, same as either of the secondary windings for example, then this situation will cause a short and blow the scope and may even cause personal injury/harm etc ,In this case, the ONLY real safe point to clip the EARTH SCOPE CLIP is any point on the DUT that is indeed at EARTH GROUND potential - but because on a device being tested for repair, that fact may not necessarily be the case hence why it is safer to eliminate the GROUND EARTH path from the DUT....
Would you say the above is accurate summary for your video?
I can see why you stated it is important to understand CLEARLY everything involved, before diving into this stuff...I am looking forward to your reply. Please correct me as necessary..
i want to thank you again - your video has helped me understand better the topic. God bless!
Great explanation!
could you pull the green wire up from the bottom of the TRANSFORMER and be ok????? i just got the same TRANSFORMER
I suppose you could as long as you understand the case is now floating and anything that is plugged in that has a third pin ground is now going to put the isolator case at that potential. Of course any type of isolation transformer for tech use is not fool proof. Cation is always needed. You could get a shock regardless of isolation depending on the unique configuration.
OK GOT IT I WILL JUST LEAVE THAT GROUND WARE ITS AT . I PICKED UP 3 OF THE SMALL PLUGS THAT WILL WORK . THANKS FOR YOUR HELP . IT MEANS A LOT
No problem.
Grounding the outlets via the screws seems like a gotcha. Guess it is always best to check for (lack of) continuity between output grounds and electrical plug ground pin or just bypass the grounds entirely by using a cheater plug.
How do you like your isolation transformer? I am looking to buy that exact model some people
say that it has a loud hum when using it..
Works fine. It has a slight hum but it is not bad. All big linear transformers hum. Don't forget the ground passes through if you are using it for tech use..
@@The_Active_Region OK thanks for info just ordered one..
@@joebiz22 You may be interested to know that the steel laminations in the transformer actually change length due to the magnetic flux. It's called magnetostriction and it happens 100 or 120 times per second depending on whether you have a 50 Hz or 60 Hz supply, so that is why all power transformers will hum.
3:10 Once you bound the neutral to the ground it is no longer an isolating transformer.
ISOLATE the DUT. Not the test equipment !
New Subscriber - I have been looking for this video for some time. Thanks so much! Bought my used scope, but have been afraid to use it on AC items after discovering this grounding issue. Also, some long time techs (12voltvids and others), tell you to float both the scope and project. So, quick questions...
Scope Earthed, Project Floating - Once you connect the ground lead from CH1 to a chassis (all channels on that scope are on the same ground), the problem is that the voltage could be different where each probe is connected (Ch1 vs CH2 potential). Is that right?
Scope Earthed, Project Earthed (To Same House Panel Ground) - It's the same ground, so why is this an issue?
I made a "dim bulb" system to use, but screwing with varying wattages is a hassle. Another story for another time.
I'm missing something still. Thx!
First answer- Once you hook up the ground on the scope to an isolated project then all scope channels will have to be attached to the same point. Unless the scope has isolated channels, which most don't.
Second answer. You can, If both are grounded then you can use the scope on the device but you have to hook up the channels from the scope to a ground on the device, "NO" where else or BOOM.
Kev31779 Thanks for your time/info.
Can I use an isolation transformer to power a modified atx bench power supply, for safe use with an oscilloscope in circuits powered by the atx supply.
I wouldn't see why not. As long as it can be isolated. I would test to make sure when it is hooked up use a multi meter and start probing potential concerns. The grounds might be the biggest issue. Always use caution when working with underground equipment and isolators. It is not code to default your grounds but in a tech modified isolater the game changes and you have to know what your actually doing to not get hurt.
“Don’t float your scope!”
LOL
A three to two, plug adapter, with an isolation transformer.
Thanks for an excellent explanation. My question: and I forgot to mention that in the USA, the safety device is called GFCI and in Australia a RCD, same thing.... so my question is: if I have a GFCI outlet supplying power to my scope as well as to the mains board I am working on,,, two separate connection but from the same GFCI outlet. Whatever I mock up on the work piece wrongly will trip the GFCI,,,,, so why do I need an I/S which only will save the scope but not my life???? I must be wrong, because everywhere I see that you need an I/T... Please help.
bro i have also been thinking about the same thing... if my test piece is being powered by Isolation trasnformer, now if I mess up on something instead of tripping the gfci its going to elelctrocute me because its isolated from the main breaker board ... I am also concerned about this...
Hint #1: if you don’t need ground pin your receptacle, go to home bipot, - and by that receptacle, witch has no ground slots on it!!! That’s how you can be 1000000000000000000% isolated from main ground!
Hint #2: if you need that pin on your receptacle, go to home depot and by that hospital rated receptacle (orange color: with green dot, or triangle) That’s how you can be 1000000000000000000% isolating from main ground!
The easy way to modify it is to replace the RECEPTACLES with ISOLATED GROUND DUPLEX RECEPTACLE PLUG OUTLET 120V 15A 20A AMP ORANGE. you can get them from ebay for about $6. The the ground hole is not connected to the mounting screws.
David Geltz That’s a BAD idea. That will just float the ground on whatever you plug into it. Do NOT flat your scope. So if you plug your scope into an outlet like this, that’s NOT good. It can NOT separate the ground tied to the neutral in the main breaker box, so you still have a path back to ground and will be electrocuted if you use this in the US. Your still at risk for injury or death. Maybe this is why it says 50Htz in the ebay ad since other counties are wired differently. Still not a good idea on a main 50Htz to use something like this, and if you have to buy an outlet for this the you don’t know enough to about mains or AC voltage and shouldn’t be testing with it. The older medical grade isolation transformers like his floats the device under test, not the testing equipment. Still not 100% safe and you can still make a mistake wiring something or using two probes but it’s safer then floating your scope.
Your best best if you don’t understand his video is buy a battery operated oscilloscope.
@@GadgetReviewVideos I think you're confused. He's not talking about floating the scope. He is talking about using a 3 prong plug from the DUT to the output of the isolation transformer replacing the existing outlet with one that has the 3rd ground hole but is not connected to earth ground.
where did you get your ac isolation transformer from?
+Ellie Okeefe I got it from Amazon..
This is getting confusing. There are many videos out there that say to isolate the oscilloscope and now this video says not to do that. Sounds like two different doctors prescribing different meds for the same condition. it sounds like you can blow up your scope no matter what step you take.
Use a battery operated test device
50 ears ago wen i become electrician and T.V epairman no ground back then on a devices or plugs but some radios ,,,and no so,,,,have 2 grounds on a shematic ( chassis ground and power supply ground ) the scope was rock up on chassis and when you want tack a dc voltage measure the ground clip go on - side of power supply , today a toilet cleaner work on electronics, BAD, VARY BAD
Doesn't anybody use differential mode any more? That way no earths are used. One channel becomes the "virtual" earth. You disconnect the earth leads from the scope probes.
Hold on a sec... If the oscilloscope is floating, then there is no path to ground so it does not matter if it's frame is at high voltage ...the issue happens when you touch both sides of the power source. ....so, it's the same issue....never bridge things with your body! Period
You always want your test equipment grounded. Period.
There's a guy here on you tube who's a professional tv tech that floats his scope. I agree with you don't do it.
You're talking about NorCal715, I noticed the same thing. Love his videos.
yes I've watched all of his videos. like the guy. He uses 2 isolation transformers one for his scope and the other for the tv he's working on.
Why spend a hundred plus dollars on an isolation transformer, that doesn't isolate the secondary?
It's probably due to regulations, but you "fix" it by removing the ground wire from the output plug.
@@Gengh13 True!
Thankyou for your explanation! This question is 100 % sincere and NOT confrontational!!!
Why? Do You Very expert, type of guys , who obviously go to great extents, to set up great
work benches, simply, go out side your home, sink an eight foot REBAR ROD into the ground,
Hook a good cable to it, and pass that cable which is an INDEPENDANT EARTH GROUND
STRICTLY FOR SAFETY BACKUP PERPOSES, TO YOUR WORK BENCH, WHICH CAN SERVE
AS A INDEPENDANT EARTH GROUND, STRICTLY FOR BENCH TESTING-----WHICH IS 100 %
ISOLATED FROM THE HOUSE MAINS NEUTRAL GOUND CIRQUIT, AS WELL AS THE EARTH
GROUND CIRQUIT WHICH IS CONNECTED TO THE PLUMBING SYSTEM AS WELL; WHICH IS
ACTUAL EARTH GROUND AS WELL; BUT IS PART OF THE MAINS AC POWER SYSTEM, AS THAT SYSTEM IS ORIGINALLY WIRED INSIDE THE MAIN POWER PANEL OF THE BUILDING?
This way, you would have an isolated path to earth gound for testing, which is completely
"Floating" as you termed it, from the main ac system of the building! ??????
What is wrong with that??? Too Much trouble???
Thankyou ! kennethzakaib607@gmail.com (AND A BIG CHICKEN THAT DOES NOT WANT TO GET BBQ-ED !!! ) THANKS!
Driving a ground into earth is not going to isolate you much. Depending on the nearest electrical grounding point and soil conditions it could conduct with the order of some resistance. Device under test using a isolation transformer and grounding test equipment is good enough if you know what your doing.
You make the bald statement that floating your oscope is bad.
Well, battery operated oscopes are floating and they work fine.
I agree if every device is connected to battery and nothing connected to your home AC outlets you should be totally protected and all devices.
We took a vote. Go back to your "multimillion dollar designs."
When you figure out why it's a bad idea to bond one leg of the secondary to the Neutral, Ground and Equipment Grounding Conductor of the primary on an isolation transformer, let me know.
That's great go ahead and float your scope. Please explain how floating a scope is much safer. They both have their caveats. The way I do i and most other techs do it the way I explained for a much less chance of self and equipment harm. Pleas do yourself a favor and tally up all the tech videos just here on TH-cam of people floating their scope vs floating the device under test.
Here is a question right out of an EE test website.
Question No. 1:You have to troubleshoot (with an oscilloscope) a piece of equipment that is mains powered and has test points at or near mains live potential. You have an isolation transformer at your disposal. Which should thed the isolation transformer power?
A The oscilloscope
B The equipment under test
C Both of them.
The correct answer is b, the equipment under test -- that will prevent it being at mains potential with respect to earth, which could be very dangerous.
Can you let it go and admit you are just plain outright wrong.
You have deleted most our comments on this subject because you are removing all my valid arguments why you are wrong. There was many many valid arguments. If you felt you were correct you would have left everything as it was in the comments to let everyone else chime in. But since I have secretly got through, you felt silly being a teacher and acting so childish when proved incorrect in the practice of the use of a "tech modified" medical isolation transformer for DUT.
Kev31779 this is why I get email notifications of comments, it gives me proof and a record of the comment they deleted, then I can copy/paste it back into the comment thread. In this comment, I wold just delete the whole comment.