Use a differential probe so you aren't referenced to anything, no problems. Dave has some video's using differential probes.
Use a differential probe so you aren't referenced to anything, no problems. Dave has some video's using differential probes.
Well surely you are referenced to the chassis ground of the oscilloscope? So if there were a 4 kV spike on one of the probes it might find a path to ground through insufficient insulation or isolation?
Use a differential probe so you aren't referenced to anything, no problems. Dave has some video's using differential probes.
Well surely you are referenced to the chassis ground of the oscilloscope? So if there were a 4 kV spike on one of the probes it might find a path to ground through insufficient insulation or isolation?
In the real world,a decent Tektronix X10 probe can be used to look at the 240v Live conductor,provided you don't connect the Grounding clip to anything & rely upon the 'scope Earthing via its own power cord to provide the return path.
In the real world,a decent Tektronix X10 probe can be used to look at the 240v Live conductor,provided you don't connect the Grounding clip to anything & rely upon the 'scope Earthing via its own power cord to provide the return path.Many of the X10 probes are rated CAT II 300V, so they should be good for up to 2.5kV anyhows....
Ground clip is the biggest safety risk for beginners and even intermediate hobbyist.
I have seen scope probes with fuse holder on ground clip in one particular company...guess they had some issues
When do all these magic 4kV spikes occur?
If they were at all common,we would have equipment being zapped everyday,all around the world.
In fact we do not,& the Power supply Companies take good care that we don't,with protective devices of various types.
Many of these very high voltage ratings are to provide a very large amount of "headroom" over & above the operating voltages of the system.
In the real world,a decent Tektronix X10 probe can be used to look at the 240v Live conductor,provided you don't connect the Grounding clip to anything & rely upon the 'scope Earthing via its own power cord to provide the return path.
And guess what? You can pre-attach the probe & then turn on the power---then,if I & the tens of thousands of other people who have used this method are wrong,all you will do is blow up your probe,or possibly your 'scope.
You will not be touching anything,so will be safe.
- HOT wire carries the current and polarity keeps changing 50 or 60 times a second only on this wire
and shows voltage when check against GROUND ?
- NEUTRAL wire is the return path
and does not carry current
and has 0V when checked against GROUND ?
I just tested the main with my fluke dmm, hot wire against ground has about 223V and neutral against ground has about 0V.
- HOT wire carries the current and polarity keeps changing 50 or 60 times a second only on this wireCorrectQuoteand shows voltage when check against GROUND ?Probably, not not necessarily. The actual mains voltage occurs between the "HOT" and the "NEUTRAL" (or "other hot" in places where they don't care!)Quote- NEUTRAL wire is the return pathCorrectQuoteand does not carry currentNO. If the neutral is the "return path", then, by definition, it carries the return current!Quoteand has 0V when checked against GROUND ?Again, that depends on the mains wiring convention in your country (or whatever). Apparently there are several competing standards for this.QuoteI just tested the main with my fluke dmm, hot wire against ground has about 223V and neutral against ground has about 0V.So that shows that in your area, you have a neutral that is connected to ground somewhere.
REMEMBER, the green-wire safety GROUND/EARTH wire DOES NOT carry current for that circuit! It is only there as a safety feature to take any fault current if something goes wrong. Else it might be going to ground through YOU!
Thank you, sounds like it's clearing up for me
So for example, say some one uses a 1000X probe rated to 10kV, he first would identify the NEUTRAL wire, put the ground of the probe on it and then probe the HOT wire to show the wave form on his DSO ?
- NEUTRAL wire is the return path and does not carry current and has 0V when checked against GROUND ?
I just tested the main with my fluke dmm, hot wire against ground has about 223V and neutral against ground has about 0V.
Thank you, sounds like it's clearing up for me
So for example, say some one uses a 1000X probe rated to 10kV, he first would identify the NEUTRAL wire, put the ground of the probe on it and then probe the HOT wire to show the wave form on his DSO ?
NO! Just because the wire is called "neutral" (or even "ground") does NOT mean that it is safe to connect the probe/scope ground to it!
If they have ANY voltage on them (more than a few millivolts of noise), relative to scope/probe ground, then it is NOT SAFE to connect the probe/scope ground! NEVER EVER connect the scope/probe ground to anything that isn't really. truly GROUND! (or is floating and it doesn't matter) The power mains neutral and even power mains safety ground are particularly hazardous because of how much current they may have behind them even if you are only measuring a volt or two. And because people just assume they are "ground" when they frequently ARE NOT (as you have shown in your own case!)
Did you not see others saying to NEVER connect the probe ground to any mains terminal? Did you not read the story of the ground clip turning white from heat? Did you not read the description of the scope probe that had a fuse in the ground wire? There are many things here that will trip you up, or blow up your scope or even electrocute you and burn down your house. This is NOT something to mess with unless you really understand what is happening here.
- NEUTRAL wire is the return path and does not carry current and has 0V when checked against GROUND ?
I just tested the main with my fluke dmm, hot wire against ground has about 223V and neutral against ground has about 0V.
Like othello says, the NEUTRAL wire carries the return current from the HOT wire.
When no current is flowing it will be at the same potential as the GROUND wire so it may appear safe however when high current is flowing, its potential will rise above GROUND and this presents a problem for grounded measurements because if the oscilloscope ground lead is attached to NEUTRAL, part of that current will flow through the oscilloscope probe, the oscilloscope, and into the oscilloscope chassis GROUND connection.
Even worse, NEUTRAL may be swapped with HOT. Almost as bad is when NEUTRAL fails for some reason like if the plug gets pulled out part way. Then the entire NEUTRAL current may flow through the ground connection of the oscilloscope probe.
In general as far as safety, it is best to treat NEUTRAL and HOT the same and off-line power supplies are not suppose to distinguish them because mistakes sometimes happen.
- NEUTRAL wire is the return path and does not carry current and has 0V when checked against GROUND ?
I just tested the main with my fluke dmm, hot wire against ground has about 223V and neutral against ground has about 0V.
Like othello says, the NEUTRAL wire carries the return current from the HOT wire.
When no current is flowing it will be at the same potential as the GROUND wire so it may appear safe however when high current is flowing, its potential will rise above GROUND and this presents a problem for grounded measurements because if the oscilloscope ground lead is attached to NEUTRAL, part of that current will flow through the oscilloscope probe, the oscilloscope, and into the oscilloscope chassis GROUND connection.
Even worse, NEUTRAL may be swapped with HOT. Almost as bad is when NEUTRAL fails for some reason like if the plug gets pulled out part way. Then the entire NEUTRAL current may flow through the ground connection of the oscilloscope probe.
In general as far as safety, it is best to treat NEUTRAL and HOT the same and off-line power supplies are not suppose to distinguish them because mistakes sometimes happen.
Thank you for the extra info on this !
What would be the official way to display highvoltage A/C waveforms on a DSO ? Not looking to cheat on costs, so just how would one go about it in a professional way ?
What would be the official way to display highvoltage A/C waveforms on a DSO ? Not looking to cheat on costs, so just how would one go about it in a professional way ?
1400Vpp is peak to peak, so half wave would be 700V ? And the 25Mhz is plenty i assume because here the household AC is 50Hz ?
When do all these magic 4kV spikes occur?
If they were at all common,we would have equipment being zapped everyday,all around the world.
In fact we do not,& the Power supply Companies take good care that we don't,with protective devices of various types.
Many of these very high voltage ratings are to provide a very large amount of "headroom" over & above the operating voltages of the system.
In the real world,a decent Tektronix X10 probe can be used to look at the 240v Live conductor,provided you don't connect the Grounding clip to anything & rely upon the 'scope Earthing via its own power cord to provide the return path.
And guess what? You can pre-attach the probe & then turn on the power---then,if I & the tens of thousands of other people who have used this method are wrong,all you will do is blow up your probe,or possibly your 'scope.
You will not be touching anything,so will be safe.
No you would not the high voltage transients are either filtered or suppressed by the inputs of your appliances. Scope probes do not have such suppression because it would corrupt the test signal. They do have input protection but that just tries to clamp the signal at their theoretical maximums.
+1. For Darwinism.
1400Vpp is peak to peak, so half wave would be 700V ? And the 25Mhz is plenty i assume because here the household AC is 50Hz ?
You should really consider an electricity course. Relation between 220VAC RMS and Vpp is "square root of 2". So in your case if you need to need to go backwards its 1400 / 1,41 -> 992,9VAC RMS.
25Mhz will suffice to check a plain 220V sinewave. Once the waveform starts to deform (eg. motor voltages, triac voltages), the high frequency harmonics start to come into play. Look up harmonics and bandwidth, read up onto this..
Knowledge is power!
When do all these magic 4kV spikes occur?
If they were at all common,we would have equipment being zapped everyday,all around the world.
In fact we do not,& the Power supply Companies take good care that we don't,with protective devices of various types.
Many of these very high voltage ratings are to provide a very large amount of "headroom" over & above the operating voltages of the system.
In the real world,a decent Tektronix X10 probe can be used to look at the 240v Live conductor,provided you don't connect the Grounding clip to anything & rely upon the 'scope Earthing via its own power cord to provide the return path.
And guess what? You can pre-attach the probe & then turn on the power---then,if I & the tens of thousands of other people who have used this method are wrong,all you will do is blow up your probe,or possibly your 'scope.
You will not be touching anything,so will be safe.
No you would not the high voltage transients are either filtered or suppressed by the inputs of your appliances. Scope probes do not have such suppression because it would corrupt the test signal. They do have input protection but that just tries to clamp the signal at their theoretical maximums.
+1. For Darwinism.
Mains supplies have been around for many years.
Only comparatively recently have devices had such protection,& even now,not every piece of equipment has protection---legacy stuff,kitchen appliances,etc.
Huge voltage spikes on the Mains supplies are incredibly rare,& even in the unlikely event of them occurring,most are of such short duration,as to (1) have very little energy, (2)be substantially attenuated by the inline inductance & resistance of the distribution system.
We have to synchronise you looking at the Mains with your 'scope,& the very rare occurrence of a spike capable of damaging your probe.
It's like winning the Lotto every day for 20 years!
For some reason,some people like to think our occupation is incredibly dangerous.
There are dangers,but a little forethought can allow you to work safely for a whole career.
Running around squawking like Chicken Little,on the other hand,is pretty much counter-productive.
Are you using the magnanimous "our", or are you trying to imply we are in the same field? By you statement I can assure you that we do not have similar work experience.
40years "hands on" in Electronics,mainly in the field of high power Transmitting equipment.--------Your turn!
As a person that needed to scope up to 145kv regularly the principals are a all the same.
25Mhz will suffice to check a plain 220V sinewave.
25Mhz will suffice to check a plain 220V sinewave.Nitpick time. Ever since the line voltage harmonization, all of EU is required to provide a nominal 230V instead of the 220V that was previously commonplace in most of Europe. I can almost guarantee you that your socket will provide you with 230 V +/-1% in practice, even if the standard allows for +10%/-6%.
I'm glad that you don't dispute the technical baggage of what i said. And yes, you are right. It was changed to 230V, a habit of speech i guess.. Allows for more power throughput though, was a nice move from the EU.