No one says that a device that has no earth connection cannot pass EMC. Only that once it was designed in such way that it needs ground connection, you should not cut that ground wire.So we seem to have debunked that earth connection is necessary to pass EMC, becasue 2 wire smps's with no earth connection still pass EMC.
Almost universally all old analog scopes have metal cases. All new ones even though the case is plastic have at least the probe ground and usually a spare ground post. Telling someone not to touch what should be at ground potential so they don´t get shocked is madness...................i've never seen a scope with a metal case........they all have plastic cases
I didn´t say that. Sniping out ground right at the scope gives you only one fifth of the current I posted before, which will give you a mild shock. I still don´t see any reason apart from being cheap why would one want to get 60V shock each time he touches a scope ground.So you are saying that if i snip the earth wire out of the plug of a modern scope, then plug it in, then touch the scope probe's ground tip, then i will definetely be electrocuted?
........i actually don't think so, i think that scope that zapped me (which i previously described) had been dropped hundreds of times, and i was just seeing if someone had a similar story, and could proove that it was earth snipping that caused it.......
For a 1000 W 13.56 MHz tube transmitter, I won't and can't snip the third prong because the load is firmly grounded unless it's a dummy load. I also cant do it if the device (another one) requires 70 Amps, 3 phase to operate.
I didn´t say that
I didn´t say that. Sniping out ground right at the scope gives you only one fifth of the current I posted before, which will give you a mild shock. I still don´t see any reason apart from being cheap why would one want to get 60V shock each time he touches a scope ground.
if the company makes power supplies or other mains equipment and needs to measure it accruately, it should simply be considered a must-have.
And what is wrong with that? You want the metal cases of anything to be tied to ground at all times. In any circuit, the only connection between a neutral and ground should be at the breaker panel. See this **broken link removed** The AC power is isolated, but the case still remains grounded. This way you can safely put the ground lead of your scope anywhere in the circuit and measure what you want. If the device you measure has a connection between neutral and ground it´s design is wrong and it should not pass any regulation.you tend to find that isolation transformers have the earth taken through to the output socket though.........and therefore, you have no choice other than to snip the earth wire out of the mains plug that you use to plug in the isolation transformer.
low power SMPS can gset away without a ground because the common mode current is below the thresholds mandated by regulatory agencies..
So we seem to have debunked that earth connection is necessary to pass EMC, becasue 2 wire smps's with no earth connection still pass EMC.
I can tell you that i worked for some of the world's biggest companies in the fields of lighting electric drives and TV sets...........and earth snipping is standard practice amongst all engineers................if an engineer went to the boss and refused to do a job because he had no isolation transformer or no differential probe, he would not be working as an engineer in these companies for long..........he would be transferred to work in "administrative duties" or basic work, etc etc.
Have you seen the cost of differential probes?....its horrendous.
I remember a contractor coming in and telling our boss off for having us all do earth snipping.............they sacked him at the end of the week.
s
In all of the Western countries, you could sue the company for wrongful termination and win.
What are the parasitic properties of an isolation transformer?
Y rated caps are used where there is a possibility of electrical shock when, and they are self-healing - will not fail shorted, typically from phase and neutral to ground. https://www.electro-tech-online.com/custompdfs/2013/01/EvoxRifaRFIandSMD.pdfThe capacitors to earth that help reduce noise could easily fail to short circuit.
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