How to mesure 240V AC with an oscilloscope

[rob77]

i never felt like i need to probe the mains with a scope (why the hell would i ?). but checking the waveform of a inverter is a different story - that makes sense.

but anyways:

1. isolation transformer !  isolation transformer .... ah... and forgot to mention... isolation transformer !
2. differential probe
3. use a battery powered scope

checking the mains waveform with a wall-wart transformer or any step-down transformer is a very good idea ! (and actually it's the solution #1 - isolation transformer)

not using isolation transformer makes you a very good candidate for the Darwin award the difference of potentials between neutral and ground might be several volts - enough to cook your scope's ground paths. if you connect your ground clip to the live by accident ... welll... you could make  a much cheaper fireworks  , rather than making one out of your scope

[David Hess]

you will blow up the mains differential if earth and ground are connected
so either use a 10x or 100x probe and cut the earth ( use a 2 prongs wire or an adaptor)
or buy a differential probe (around 100€ you can find on the bay)
see dave's video as said earlier in this thread is a good start anyway.

cut the earth from scope or DUT?
is it safe?

It is not considered safe.
Read the attached document ex Tektronix.

What I always thought funny is the older Tektronix application notes recommending this very method.  I think it is even used in some of their old service manuals.

As far as cutting the earth ground to the device under test and using an isolation transformer with it, that does not preclude attaching earth ground to the point where the oscilloscope probe is grounded as long as it is neutral or the chassis.

[saturation]

For working on such tasks you are best off with a portable scope or a differential probe; there are industrial grade active probes that are relatively low cost made for checking appliance grade electronics, these are made by testec or tiepie and resold under different brand names.

http://www.testec.de/tastkoepfe_25mhz.0.html?&L=1

There is also a similarly priced Taiwanese version sold also by many brands.

http://www.pintek.com.tw


The above come in various bandwidths for price, all are sold under many brand names.

[othello]

Although i never tried to measure mains AC with a scope, what would be the preferred way to do it ? My scope for example is rated at 300V RMS, so i assume 220V RMS should be no problem when using a 10x probe ? I read the probe specs and their rating says for 10X: CAT II 300V AC. But unlike the scope manual, the probe specs don't mention RMS. Is it still safe to use the probe in 10x mode to measure 220V RMS ? So lets say i'm looking at the wires coming out of the wall, 3 wires, 1 is earth. How would you make connection to measure using the 10x probe ? Scope itself is grounded, bench scope.

PS: sorry for the newbie questions, appreciate your guidance

[Richard Crowley]

If someone held a gun to my head, I would use a 10x probe. First I would leave the scope probe ground FLOATING! 

Then I would probe green-wire safety ground to see how much difference there is between the oscilloscope ground reference and the mains safety ground. That measurement by itself would be interesting. Then I would probe the "neutral" ("cold") side to see what is the differential between THAT and scope reference ground.

THEN I would consider poking the probe at the hot side of the mains (with the scope set for the expected peak-to-peak voltage we expect based on the nominal voltage.  i.e. 679 VAC P-P for a nominal "240V power mains.  Even at nominal 120V mains voltage where I live, I would only probe the hot side if you pulled the hammer back on the pistol as an additional threatening gesture.

I STILL don't get the morbid fascination with people here probing the power mains with their oscilloscopes!  As far as I can see. it is an adult extension of what small infants do when they poke things into the wall outlets. 

At the risk of repeating myself: If I want to know the mains VOLTAGE, then I will use a proper DMM. If I want to look at the WAVEFORM of the power mains, I will grab a discarded wall-wart transformer, and safely probe the low-voltage secondary.

[kripton2035]

At the risk of repeating myself: If I want to know the mains VOLTAGE, then I will use a proper DMM. If I want to look at the WAVEFORM of the power mains, I will grab a discarded wall-wart transformer, and safely probe the low-voltage secondary.

the problem with wall mart transformers is that they are made for 50-60Hz frequency
if you want to look at x10 signals around 100KHz, there is not a lot of anything to look at !

[Richard Crowley]

At the risk of repeating myself: If I want to know the mains VOLTAGE, then I will use a proper DMM. If I want to look at the WAVEFORM of the power mains, I will grab a discarded wall-wart transformer, and safely probe the low-voltage secondary.

the problem with wall mart transformers is that they are made for 50-60Hz frequency
if you want to look at x10 signals around 100KHz, there is not a lot of anything to look at !

People with such legitimate requirements....
1) can characterize some transformers and screen them for HF response. It is not unusual for a small transformer to have response to 100KHz.
2) can high-pass filter the tap to allow looking at the HF content while minimizing the hazardous energy from the baseband frequency.
3) probably can afford and know how to safely use the proper equipment to do the job without risk.
4) probably aren't asking such random questions with no apparent motivation in the beginner's forum.

Advising people with dubious experience and unknown endowments common sense on messing safely with power mains has been a problem in electronics-related forums since the beginning of Usenet. And the special concentration on test equipment in this forum makes the problem even more prominent here.  I am just very concerned about many newbies who come though here innocently asking about doing dangerous things. I guess that is why we have the Darwin Awards.

[BravoV]

3) probably can afford and know how to safely use the proper equipment to do the job without risk.

+1

Though not an expert, imo when it comes to mains line related voltage probing, its time to talk about isolated probing techniques.

Each method has it's advantages and trade offs, click here -> HERE and download the Tektronix "Fundamental of Floating Measurements and Isolated Input Oscilloscopes".

Yes, its not cheap when it comes to a "proper" high voltage and isolated probing using an oscilloscope.    ... sigh

Fyi, a battery powered or handheld scope does NOT mean they're isolated scope, it must be designed from the 1st place, from the scope down to the probes, thats why usually they're quite pricey. 


A nice example illustration on how an isolated scope was designed, stolen from Tektronix.



Simple example below on what you can do with an isolated scope, just watch carefully the different hook points at "both probes ground clips", its just impossible to do that with an ordinary 2 ch scope, even using an isolated transformer or floated scope/dut, or handheld/battery powered scope that is NOT designed as an isolated scope from the beginning.

Just be careful before using the scope on mains line without a clear & through understanding on the details and dangerous involved, its not worth your life especially just for the sake of curiosity. 

[BillWojo]

That TekScope print that you borrowed, does that pertain to older Tektronixs scopes as well such as my 465M? I'm troubleshooting a DC motor drive from the 50's that uses a pair of C16J thyratron tubes, lot's of nasty DC voltages involved. I picked up a 100X probe and an electrical tech that I know gave me a few very small value caps, said to put one of the caps between the ground clip and one end of the circuit. Ground lead to filiment and test lead to grid. Might not be 100% correct on that, my notes are not with me.

BillWojo

[Muanpuia]

Please anybody know where to buy refurbished/used scope for a very cheap price? Too costly for me to buy in my country. Its kind of suffocating sometimes just reading about it and planning what id do with it. Im using my soundcard for almost three years now and when i try using it for digital realm its mostly impractical to multiplex/filter it around. The result i get hardly makes sense. It seems these days most are digital and atleast those old CRO would still be somewhere out of service...

[othello]

If someone held a gun to my head, I would use a 10x probe. First I would leave the scope probe ground FLOATING! 

Then I would probe green-wire safety ground to see how much difference there is between the oscilloscope ground reference and the mains safety ground. That measurement by itself would be interesting. Then I would probe the "neutral" ("cold") side to see what is the differential between THAT and scope reference ground.

THEN I would consider poking the probe at the hot side of the mains (with the scope set for the expected peak-to-peak voltage we expect based on the nominal voltage.  i.e. 679 VAC P-P for a nominal "240V power mains.  Even at nominal 120V mains voltage where I live, I would only probe the hot side if you pulled the hammer back on the pistol as an additional threatening gesture.

I STILL don't get the morbid fascination with people here probing the power mains with their oscilloscopes!  As far as I can see. it is an adult extension of what small infants do when they poke things into the wall outlets. 

At the risk of repeating myself: If I want to know the mains VOLTAGE, then I will use a proper DMM. If I want to look at the WAVEFORM of the power mains, I will grab a discarded wall-wart transformer, and safely probe the low-voltage secondary.

Thank you for the advise ! It's better to at least know than to stay ignorant so i hope you don't mind the questions.

1. I've measured the DSO ground ref with the mains ground (earth i assume), difference is about 1.3V, what does that tell me ?
2. If you talk about "neutral" and "hot", you mean the earth of the mains and one of the hot wires ?
3. I take it that a 100x probe is safer than a 10x probe ? Why if the 10x is rated 300V AC CAT II and DSO INPUT IS 300V AC RMS ?
4. With "FLOATING" does it mean leave the ground wire unconnected of the probe itself ?
5. Say i have a 100X probe, i assume i connect the ground of the probe to the earth wire and then probe one of the hot wires ?

Thank you again, just want to understand more about measuring AC and do's and don'ts without doing it :-)

[WarSim]

This topic was intertwining I must say. 

Only once was there any query to clarify the test aspect requirements.  As a person that needed to scope up to 145kv regularly the principals are a all the same. 

For specific reasons different probing methods and probe types are used.  Yes there is a difference safety gear when using x1 and x10,000 probes but the principles and safety are the same. 

All I read here is is a lot of people who have gotten complacent with their probe use skills because they only measure what they consider low voltage. 

There have been recorded deaths from as little as 10ma and 12v.  I wouldn't be surprised that there are others I don't know about. 

[Richard Crowley]

1. I've measured the DSO ground ref with the mains ground (earth i assume), difference is about 1.3V, what does that tell me ?

It means that already you have 1.3V difference between what SHOULD be mains ground and what the scope thinks is "ground".
There are a dozen unknowns here that prevent more detailed analysis of this finding.  For example:
1) What is the grounding scheme in your (unidentified) scope?  Does it have a 3-pin, grounded mains plug?
2) What is the connection between the power mains green-wire ground and the chassis/case ground of your scope?
3) What is the connection between the scope chassis and the outside shell/ground/reference of the probe input(s)?
4) How familiar are you with the power mains conventions in your country?  WHERE are you?
5) You don't sound very sure about exactly where you probed.  Did you really probe the green-wire ground?  Or the white (or blue?) wire neutral/low side?
6) Did you probe the same outlet where the scope is plugged in?
7) How good is the wiring to that power outlet?  Faulty and/or degrading wiring will cause the ground and/or neutral nodes to rise above 0V ground.

2. If you talk about "neutral" and "hot", you mean the earth of the mains and one of the hot wires ?

Low/Cold/Neutral is NOT the same as the green-wire safety ground.  At least in most of the civilized world. But again, we don't know where you are?

You might want to learn more about how power mains are wired before going anywhere near them with a scope probe.
Now if you want to use a DMM of appropriate specs to investigate the voltages on various power mains nodes, that would be orders of magnitude safer for both you and for your equipment.  If it rather scary to hear you wanting to probe something that dangerous, but which you seem to not understand yet.

3. I take it that a 100x probe is safer than a 10x probe ?

A 100x probe can likely take a higher voltage than a 10x probe. But that is relative, and you live in a Real World.

Why if the 10x is rated 300V AC CAT II and DSO INPUT IS 300V AC RMS ?

300V is not high enough to consider going anywhere near the hot side of a mains source.

4. With "FLOATING" does it mean leave the ground wire unconnected of the probe itself ?

It means that while the BNC connector on the scope grounds the shield around the probe wire, you leave the ground node out at the end of the probe NEVER touching anything.

5. Say i have a 100X probe, i assume i connect the ground of the probe to the earth wire and then probe one of the hot wires ?

NO!  That would assume that the earth wire is at zero volts relative to the scope ground. You have already shown that is NOT the case!
That is where you start getting into trouble here.  You CAN NOT assume that the "earth wire" is the same ground as the scope reference.
Some of the reasons are those questions up at the top of this post. And those are just the most obvious questions. There are dozens more.
This is NOT as simple as you might want it to be.  This is a complex and DANGEROUS proposition and you would do well to take a much more cautious approach.

[vk6zgo]

If someone held a gun to my head, I would use a 10x probe. First I would leave the scope probe ground FLOATING! 

Then I would probe green-wire safety ground to see how much difference there is between the oscilloscope ground reference and the mains safety ground. That measurement by itself would be interesting. Then I would probe the "neutral" ("cold") side to see what is the differential between THAT and scope reference ground.

THEN I would consider poking the probe at the hot side of the mains (with the scope set for the expected peak-to-peak voltage we expect based on the nominal voltage.  i.e. 679 VAC P-P for a nominal "240V power mains.  Even at nominal 120V mains voltage where I live, I would only probe the hot side if you pulled the hammer back on the pistol as an additional threatening gesture.

I STILL don't get the morbid fascination with people here probing the power mains with their oscilloscopes!  As far as I can see. it is an adult extension of what small infants do when they poke things into the wall outlets. 

At the risk of repeating myself: If I want to know the mains VOLTAGE, then I will use a proper DMM. If I want to look at the WAVEFORM of the power mains, I will grab a discarded wall-wart transformer, and safely probe the low-voltage secondary.

Thank you for the advise ! It's better to at least know than to stay ignorant so i hope you don't mind the questions.

1. I've measured the DSO ground ref with the mains ground (earth i assume), difference is about 1.3V, what does that tell me ?
2. If you talk about "neutral" and "hot", you mean the earth of the mains and one of the hot wires ?
3. I take it that a 100x probe is safer than a 10x probe ? Why if the 10x is rated 300V AC CAT II and DSO INPUT IS 300V AC RMS ?
4. With "FLOATING" does it mean leave the ground wire unconnected of the probe itself ?
5. Say i have a 100X probe, i assume i connect the ground of the probe to the earth wire and then probe one of the hot wires ?

Thank you again, just want to understand more about measuring AC and do's and don'ts without doing it :-)

IF you live in most countries,your Electricity company supplies you with your house power at 240v,220v,or 120V,or whatever,in the form of Live (also called "Active' or "hot") & Neutral conductors.

The Neutral may,or may not be physically grounded elsewhere,depending on the exact system,but it is almost always physically grounded at the entrance to your house.
From the point this is done,a third ground,or "Earth" conductor is extended to your power point.

At the power point (called a "GPO" in Australia,so for convenience I will use that terminology),there are normally two similar socket  holes,& a third "different"one.

For instance,an Australian GPO has two slanted flat pins above one vertical one.

At first sight,grounding one side of the Mains seems mad,as there are many incidentally grounded objects in the average house,so you could get between them & Live & be zapped,but there is "method in their madness".

Historically,most Electrical appliances had metal cases,for strength,as plastics were not sufficiently developed.
Imagine with a system where neither Mains conductor was grounded,& two such devices developed short circuits between opposite conductors & the metal case.
Both devices would continues to work OK individually,but there would be,say 220V between the cases.

If you were happily working in the kitchen & touched both devices,you would be "toast",as the Mains fuses wouldn't notice the small increase in current draw needed to cook you!

Enter the three wire "protective Earth' system.

A short develops between the case & the Active conductor----- the Earth conductor is connected back to the Neutral side  at the house entry point,so the Power supply sees a dead short,excessive current flows,the fuse in the fusebox blows,& you are protected.

In an ideal world,"Earth" & Neutral" would always be at exactly the same potential.no matter what GPO you looked at,but in the real world,Neutral has to carry the same current as the Live conductor,whereas the Earth does not,so there will be some voltage drop,hence the difference in voltmeter reading. between the two at any given GPO.

Let's look at (2)"If you talk about "neutral" and "hot", you mean the earth of the mains and one of the hot wires ? "
From the above you can see that "NEUTRAL" & "Earth" are not the same thing.
"Neutral" & "hot" means exactly the same thing as "Neutral" & "Live".

There are two special cases where referring to the two pins on a power outlet as both "hot" is legitimate.-

(a)When you are looking at an old installation where you do not know which output of the GPO is the Live one----for instance,the now mandatory connection of Live as the left socket pin & Neutral as the right one was only a "recommendation" in Australia until the 1970s.

(b) In the USA,some appliances require 240v as distinct from the normal 120v supply.
This is done using a special transformer on the power pole which has a 240v secondary .
The secondary is centre tapped to produce two Live 120v feeds,with the tap as Neutral.
At a 240v socket,there are now  two LIve 120v socket holes & one Neutral.
The device is connected between the two "hots" & hence across the 240v secondary of the transformer.

Re (4):-
Oscilloscopes normally have one side of the 'scope inputs returned to the metal case and/or internal metalwork of the instrument, hence, via the power cord, GPO & internal wiring to where the Earth & Neutral are connected.
If you completely remove the grounding lead from a 'scope probe & probe the "Active" you will ne able to see  the Mains waveform,as the return side of the probe's circuit is provided by the instrument  Earth as described above.

This is what Richard referred to as "Floating",as he has pointed out in his later posting.

[tautech]

As a person that needed to scope up to 145kv regularly the principals are a all the same.

WOW, I am in awe. 
Tell us more please.

[WarSim]

As a person that needed to scope up to 145kv regularly the principals are a all the same.

WOW, I am in awe. 
Tell us more please.

Here is all the info I can offer.  The RADAR systems I worked on needed needed to be maintained and tuned so it don't go boom. 

[tautech]

As a person that needed to scope up to 145kv regularly the principals are a all the same.

WOW, I am in awe. 
Tell us more please.

Here is all the info I can offer.  The RADAR systems I worked on needed needed to be maintained and tuned so it don't go boom. 

OK, by your profile , I guess military application. 
But 145 kV and 10,000:1 probes. 

[WarSim]

actually nick is from an AI I wrote, in 1990.  But yes some had militarized applications. 

Yeah the huge 10,000:1 probe with matching cuffs, helmet and boots.  Very stylish

[mzzj]

3. I take it that a 100x probe is safer than a 10x probe ? Why if the 10x is rated 300V AC CAT II and DSO INPUT IS 300V AC RMS ?

Mostly because 100x probes usually don't have switch like many 10x probes that you can accidentally switch to 1x position.

10x is rated 300V AC CAT II Probe FROM RELIABLE MANUFACTURER is good enough for probing mains at your workshop table.
CAT II probe must be able to withstand up to 2500v surge peaks from the mains. 
Your average scope input will get fried with that 2500v surge. 

http://digital.ni.com/public.nsf/allkb/05D3F9C0F740BC2986256E9A00505421

[tautech]

10x is rated 300V AC CAT II Probe FROM RELIABLE MANUFACTURER is good enough for probing mains at your workshop table.

   
What people fail to remember in posts, is mains voltages vary on this planet and IMO it would be unwise to use any 300 V rated probe or scope near 230 VAC mains, CAT rated or otherwise.

Consider a simple 230 VAC SMPS, rectified mains for the primary switcher is ~325 V DC.
You already exceed the probe voltage rating!

IMO if you do not have at least 600 V 10:1 probes you are at risk.
Even this will not give you much headroom when it comes to voltage de-rating with frequency.

Better that you have at least one 100: 1 probe because safety demands it.

[othello]

Thank you all for the valueable input !

After reading it seems a few more questions came up. For clearity, i'm not going to probe mains with my DSO, don't know enough about high voltage / dangerous currents vs safety. But if i would have to do it in the future, how would i do it, in practical terms ?

Here is some info which applies to my situation and can be used as example:

- Country: The Netherlands
- Mains voltage: 220V AC (my DMM says 222V AC)
- DSO Rigol 2202  (300V AC CAT I) ,
- Probe 10X/1X (300V AC CAT II)
- I have a surgeprotector from APC which shows a green led if the earth connection is good, it shows green.


So i'm look at a normal socket in the house, 3 wires are coming out of it as follows;

- 2 wires are hot
- 1 wire is earth

Q1: Now about the above, the wire i call earth should i call it ground or neutral ? Or what is the official word for it ?
Q2: The 2 wires i call hot, should i call them live or what is the official word to call those 2 ?

Measuring with my DMM 1 hot with earth wire shows 0V, same for the other hot wire with earth, also 0V.
Measuring with my DMM the 2 hot wires gives about 222V AC.

Situation with the DSO:

- Bad idea to use a 10X from what i read
- Good idea to use a 100X probe

Q1: At the front of the DSO there is a ground hook (?), i measured with the DMM a difference between that ground hook and the earth wire from the wallsocket of about 1.3V. In practise, does this mean i'm dead if i use a 100x probe to try and display the waveform on the above DSO (see specs) ?
Q2: Is it correct to connect the 100x probe ground to the earth wire of the wallsocket and then probe one of the hot wires ? If not, what is the best way to do it ?

Situation ESD work (not directly related to above situations btw):

- Anti-static wrist strap

Q1: The proper way is to put it on then connect the wire to the earth clip of the wallsocket, is this correct ?


Hope you guys have some patience and help me understand in practical words the answers you give to the above.

Thank you !

[Ribster]

Reading your post, i would discourage you to do anything with mains voltage.
If you do want to power something from mains, for your own safety, use a separating transformer (Dutch: Scheidingstransformator).
It's a simple transformer that converts 220V to 220V. So a transformation of 1:1.
This is a safer situation. If you short out the secondary, the consequences will be less dangerous.

[Richard Crowley]

- Country: The Netherlands

It would be convenient if you could complete your user profile to at least identify your country so we have some clue what you are talking about.

- Mains voltage: 220V AC (my DMM says 222V AC)

REMEMBER that is RMS, and peak-to-peak voltage is CONSIDERABLY higher than that!!!!!

- DSO Rigol 2202  (300V AC CAT I) ,
- Probe 10X/1X (300V AC CAT II)

300V is NOT adequate to probe the peak-to-peak voltage you would expect from ANY mains supply.

- I have a surgeprotector from APC which shows a green led if the earth connection is good, it shows green.
So i'm look at a normal socket in the house, 3 wires are coming out of it as follows;

- 2 wires are hot
- 1 wire is earth

If truly "2 wires are hot" then your surge protector would have no frame of reference to tell "if the earth connection is good".
I don't know anything about how the mains power is distributed in your country, but I question whether "2 wires are hot".
You REALLY REALLY need to study exactly how mains power wiring is done in your country. THIS IS NO PLACE FOR GUESSWORK AND ASSUMPTION!!!!!

Q1: Now about the above, the wire i call earth should i call it ground or neutral ? Or what is the official word for it ?
Q2: The 2 wires i call hot, should i call them live or what is the official word to call those 2 ?

Measuring with my DMM 1 hot with earth wire shows 0V, same for the other hot wire with earth, also 0V.
Measuring with my DMM the 2 hot wires gives about 222V AC.

Clearly your measurements show that you do NOT have "2 wires are hot".
If you are measuring 0V from a "hot" wire to earth, then it is either BROKEN, or else it is not "hot".

PLEASE PLEASE study how mains wiring is done in your country before putting your equipment or yourself any more at risk!

Situation with the DSO:

- Bad idea to use a 10X from what i read
- Good idea to use a 100X probe

Until you know more about mains wiring these are BOTH a bad idea.

Q1: At the front of the DSO there is a ground hook (?), i measured with the DMM a difference between that ground hook and the earth wire from the wallsocket of about 1.3V.

As we already discussed, without knowing more about the situation, we cannot make any definitive diagnosis from this symptom.

In practise, does this mean i'm dead if i use a 100x probe to try and display the waveform on the above DSO (see specs) ?

It is probably safe if your remember to NOT connect the scope/probe ground to ANYTHING!!!!

Q2: Is it correct to connect the 100x probe ground to the earth wire of the wallsocket and then probe one of the hot wires ?

NO!  You repeatedly report that you are seeing ~1.3V difference between the scope/probe ground and the mains earth/cold/neutral.
What do you expect to happen when you connect that to the scope/probe ground?  If that is caused by faulty wiring or an overloaded circuit, that could FRY your scope!

If not, what is the best way to do it ?

First, learn how mains power wiring is supposed to be done in your country.
Then, analyze your mains circuit to see why it is showing 1.3V difference where there should be 0.0 V
Then, give us a better definition of exactly what you are trying to accomplish by probing the mains power?

Situation ESD work (not directly related to above situations btw):
- Anti-static wrist strap
Q1: The proper way is to put it on then connect the wire to the earth clip of the wallsocket, is this correct ?

Suggest searching the archives. I must assume this has been discussed before.

[othello]

Reading your post, i would discourage you to do anything with mains voltage.
If you do want to power something from mains, for your own safety, use a separating transformer (Dutch: Scheidingstransformator).
It's a simple transformer that converts 220V to 220V. So a transformation of 1:1.
This is a safer situation. If you short out the secondary, the consequences will be less dangerous.

Thanks, i read indeed about isolation transformers. Their secondary is still 220V AC but ungrounded ?

[othello]

- Country: The Netherlands

It would be convenient if you could complete your user profile to at least identify your country so we have some clue what you are talking about.

- Mains voltage: 220V AC (my DMM says 222V AC)

REMEMBER that is RMS, and peak-to-peak voltage is CONSIDERABLY higher than that!!!!!

- DSO Rigol 2202  (300V AC CAT I) ,
- Probe 10X/1X (300V AC CAT II)

300V is NOT adequate to probe the peak-to-peak voltage you would expect from ANY mains supply.

- I have a surgeprotector from APC which shows a green led if the earth connection is good, it shows green.
So i'm look at a normal socket in the house, 3 wires are coming out of it as follows;

- 2 wires are hot
- 1 wire is earth

If truly "2 wires are hot" then your surge protector would have no frame of reference to tell "if the earth connection is good".
I don't know anything about how the mains power is distributed in your country, but I question whether "2 wires are hot".
You REALLY REALLY need to study exactly how mains power wiring is done in your country. THIS IS NO PLACE FOR GUESSWORK AND ASSUMPTION!!!!!

Q1: Now about the above, the wire i call earth should i call it ground or neutral ? Or what is the official word for it ?
Q2: The 2 wires i call hot, should i call them live or what is the official word to call those 2 ?

Measuring with my DMM 1 hot with earth wire shows 0V, same for the other hot wire with earth, also 0V.
Measuring with my DMM the 2 hot wires gives about 222V AC.

Clearly your measurements show that you do NOT have "2 wires are hot".
If you are measuring 0V from a "hot" wire to earth, then it is either BROKEN, or else it is not "hot".

PLEASE PLEASE study how mains wiring is done in your country before putting your equipment or yourself any more at risk!

Situation with the DSO:

- Bad idea to use a 10X from what i read
- Good idea to use a 100X probe

Until you know more about mains wiring these are BOTH a bad idea.

Q1: At the front of the DSO there is a ground hook (?), i measured with the DMM a difference between that ground hook and the earth wire from the wallsocket of about 1.3V.

As we already discussed, without knowing more about the situation, we cannot make any definitive diagnosis from this symptom.

In practise, does this mean i'm dead if i use a 100x probe to try and display the waveform on the above DSO (see specs) ?

It is probably safe if your remember to NOT connect the scope/probe ground to ANYTHING!!!!

Q2: Is it correct to connect the 100x probe ground to the earth wire of the wallsocket and then probe one of the hot wires ?

NO!  You repeatedly report that you are seeing ~1.3V difference between the scope/probe ground and the mains earth/cold/neutral.
What do you expect to happen when you connect that to the scope/probe ground?  If that is caused by faulty wiring or an overloaded circuit, that could FRY your scope!

If not, what is the best way to do it ?

First, learn how mains power wiring is supposed to be done in your country.
Then, analyze your mains circuit to see why it is showing 1.3V difference where there should be 0.0 V
Then, give us a better definition of exactly what you are trying to accomplish by probing the mains power?

Situation ESD work (not directly related to above situations btw):
- Anti-static wrist strap
Q1: The proper way is to put it on then connect the wire to the earth clip of the wallsocket, is this correct ?

Suggest searching the archives. I must assume this has been discussed before.

Thanks for the advise Richard ! Just to clarify, i'm not planning or touching anything AC. Only asking your views / advise.

The reason why i call those 2 wires hot is that polarity doesn't matter with AC mains. So both wires are dangerous unless i'm wrong in assuming so.
The 3rd wire is earth, but i don't understand why i would only have 1 of those 2 wires called hot and not both called hot ? I'm guessing this is where i'm confused about thinking of polarity for those AC wires and assuming both are dangerous ...

Example:

Lightbulb connected to those 2 wires, changing wires doesn't matter. That is why i call them both hot