Re: Stop messing around guys
And if you lick a 9V battery there is a chance your heart could stop. So what. If you have read the thread then you would know the question posted was "when do I need to use a transformer to isolate my scope". Question was anwered and the obligatory warnings were made about watching out for high voltages and caps holding a charge after power down. Some others made futher suggestions of possible ways to improve safety, but the truth is you just have to be careful. Doing stuff like keeping one hand in your pocket (or wearing a rubber glove on your off hand) means that when you mess up you are a lot more likely to get scared rather than killed. Is this a bad thing?
Or do you recommend we hire a licensed electrician to set the bias current in our class A amps? I'd like to see the look on his face when you ask him how much he charges for that.
P.S. I am an EE and before getting my degree I worked as an electronics technician for 17 years installing and maintaining process control equipment. If you are not Harry then you are being mighty bossy for someone who just wandered in today.
Phil
Welcome back Harry.Virgil Hilts said:
And if you lick a 9V battery there is a chance your heart could stop. So what. If you have read the thread then you would know the question posted was "when do I need to use a transformer to isolate my scope". Question was anwered and the obligatory warnings were made about watching out for high voltages and caps holding a charge after power down. Some others made futher suggestions of possible ways to improve safety, but the truth is you just have to be careful. Doing stuff like keeping one hand in your pocket (or wearing a rubber glove on your off hand) means that when you mess up you are a lot more likely to get scared rather than killed. Is this a bad thing?
Or do you recommend we hire a licensed electrician to set the bias current in our class A amps? I'd like to see the look on his face when you ask him how much he charges for that.
P.S. I am an EE and before getting my degree I worked as an electronics technician for 17 years installing and maintaining process control equipment. If you are not Harry then you are being mighty bossy for someone who just wandered in today.
Phil
You are right . except compare would be a better word than sums.
You are right, BUT safety ground (or Protective Earth?) is connected to Mother Earth and that means that all things standing on her will be earth connected like concrete buildings waterpipes and every other conductive material.
Keld
Keld said:
Well, on a conceptual level, yes. I should probably uesd the word
compare. I guess I was too stuck to how these things actually
work, which is by summing the magnetic flux of two coils, one
on live, one on neutral.
In theory, but in practice it need not be so. In most cases you
are probably likely to get grounded via something which acts
as a resistor to ground. There are also many different ground
systems which do not quite agree. The ground in the electric
network need not coincide with the ground in the central antenna
network of a house, which is one of many possibilities for
accidental grounding.
Well, it seems Virgil Hilts is actually HH, since he is banned.
(I didn't think so. Lacked his ingenuity in the profile, I think,
but he probably wanted to get a chance to make a few posts
before we broke his new alias. 🙂 )
Anyway, he should be taken serious to the extent that we
are talking about very dangerous things, and one should read
up and know what one is doing. 12V is harmless, whether meant
as a joke or an exaggeration of the dangers, but the rail voltages
in a power amp can be lethal, depending on circumstances.
Don't poke around inside any equipment if you are sweating
for instance. Dry skin has a rather high resistance. Wet skin
has very low resistance, and does not go hand in hand with
electricity. NOTE, I am NOT saying it is safe just because your
skin is dry.
Hi Sam9,
I agree with Haldor - if your amp is powered from an isolating transformer, you don't need to run the scope on one. But remember the ground clip of your scope probe is connected to scope's chassis. Which is connected to the supply ground. Any part of your circuit that you attach the scopes ground clip to, will therefore be grounded. You can then use the probe tip to probe any part of your circuit, provided it has a suitable voltage rating. And you'll measure voltages with respect to ground.
I've seen people cut the ground wire on their scopes' power supply, to make pseudo-differential measurements. DON'T DO THAT! It's dangerous (metal parts of your scope float up to the voltages you're measuring). And it gives inaccurate measurements.
Something about your post made me think you might be doing that. If I'm wrong, no hard feelings. If I'm right, let me know and I'll tell you where to get a cheap differential probe (not made by my company) so you can make those measurements safely.
Cheers,
I agree with Haldor - if your amp is powered from an isolating transformer, you don't need to run the scope on one. But remember the ground clip of your scope probe is connected to scope's chassis. Which is connected to the supply ground. Any part of your circuit that you attach the scopes ground clip to, will therefore be grounded. You can then use the probe tip to probe any part of your circuit, provided it has a suitable voltage rating. And you'll measure voltages with respect to ground.
I've seen people cut the ground wire on their scopes' power supply, to make pseudo-differential measurements. DON'T DO THAT! It's dangerous (metal parts of your scope float up to the voltages you're measuring). And it gives inaccurate measurements.
Something about your post made me think you might be doing that. If I'm wrong, no hard feelings. If I'm right, let me know and I'll tell you where to get a cheap differential probe (not made by my company) so you can make those measurements safely.
Cheers,
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