Author Topic: Looking for portable oscilloscope  (Read 9999 times)

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Offline abgx1Topic starter

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Re: Looking for portable oscilloscope
« Reply #25 on: December 12, 2023, 10:15:38 am »
But was your ground completely disconnected?

I think there is some confusion and everybody is testing something else. I will try to draw a schematics...
 

Online 2N3055

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Re: Looking for portable oscilloscope
« Reply #26 on: December 12, 2023, 12:17:37 pm »


Do any of fluke's handheld oscilloscopes have a separate ground?!
Even the Fluke 190 Series III ScopeMeter doesn't include it, that is, I can't see it anywhere, even though it's a +4000 Euro instrument.
As written above, compliance with the safety regulations is the most important.


Fluke has scope with galvanically fully isolated channels from scope ground and each other.
Keysight has has scope with galvanically fully isolated channels from scope ground and each other.
R&S has has scope with galvanically fully isolated channels from scope ground and each other.
Siglent has has scope with galvanically fully isolated channels from scope ground and each other. That is most affordable one.

Those are I know of. There could be more..
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Online mikeselectricstuff

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Re: Looking for portable oscilloscope
« Reply #27 on: December 12, 2023, 12:19:18 pm »
The Micsig tablets scopes are also well worth a look.
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Online nctnico

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Re: Looking for portable oscilloscope
« Reply #28 on: December 12, 2023, 12:22:07 pm »
The Micsig tablets scopes are also well worth a look.
I agree. And they are rugged as well. Recently I dropped mine and it survived that just fine. For measuring high voltages / mains safely, you'd need a CAT rated differential probe though.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Online 2N3055

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Re: Looking for portable oscilloscope
« Reply #29 on: December 12, 2023, 12:24:43 pm »
The Micsig tablets scopes are also well worth a look.

They used to have an isolated handhelds before but not anymore.
"Just hard work is not enough - it must be applied sensibly."
Dr. Richard W. Hamming
 

Offline abgx1Topic starter

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Re: Looking for portable oscilloscope
« Reply #30 on: December 12, 2023, 01:50:57 pm »
What is the cheapes differential probe which can be used on main voltage?
 

Online nctnico

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Re: Looking for portable oscilloscope
« Reply #31 on: December 12, 2023, 02:05:44 pm »
What is the cheapes differential probe which can be used on main voltage?
Last time I checked the CAT rated ones from Micsig are the most economic ones.
« Last Edit: December 12, 2023, 02:11:32 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline shapirus

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Re: Looking for portable oscilloscope
« Reply #32 on: December 12, 2023, 02:08:21 pm »
I believe there also were some feasible DIY designs discussed on this forum (that someone actually implemented). Search should show them.
 

Offline Fungus

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Re: Looking for portable oscilloscope
« Reply #33 on: December 12, 2023, 04:34:56 pm »
What is the cheapes differential probe which can be used on main voltage?

Micsig.
 

Offline alm

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Re: Looking for portable oscilloscope
« Reply #34 on: December 12, 2023, 07:32:07 pm »
So it doesn't work. I have just verified this with a handheld battery-powered scope: when the ground clips are detached, the Ch1-Ch2 (math) waveform becomes garbage.
The signals need to stay within range for both channels. Especially with a floating scope the reference level may well be at a level away from ground, pulling the signals relative to the reference out of range. With a grounded scope this is not going happen because CH1 and CH2 are always referenced to ground. This is also a potential problem with real differential probes. Which is for example why Fluke tells you to ground the floating scope when using two differential probes at the same time.

For measuring high voltages / mains safely, you'd need a CAT rated differential probe though.
No, you don't need a differential probe. A single-ended probe designed for floating measurements will also work. It's not like the reference level is moving much relative to earth. If you read the manual for high voltage differential probes, they have statements like "make sure the oscilloscope is grounded" or "These probes are designed for use with oscilloscopes that have a common terminal at GROUND POTENTIAL". So I'd say a single-ended probe for floating measurements is a better choice for a battery-powered scope with isolated inputs (the only type of battery-powered scope I'd use on mains). Either that, or use a grounded scope with a high voltage differential scope.
« Last Edit: December 12, 2023, 07:33:55 pm by alm »
 

Online nctnico

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Re: Looking for portable oscilloscope
« Reply #35 on: December 12, 2023, 07:40:32 pm »
For measuring high voltages / mains safely, you'd need a CAT rated differential probe though.
No, you don't need a differential probe. A single-ended probe designed for floating measurements will also work. It's not like the reference level is moving much relative to earth. If you read the manual for high voltage differential probes, they have statements like "make sure the oscilloscope is grounded" or "These probes are designed for use with oscilloscopes that have a common terminal at GROUND POTENTIAL". So I'd say a single-ended probe for floating measurements is a better choice for a battery-powered scope with isolated inputs (the only type of battery-powered scope I'd use on mains). Either that, or use a grounded scope with a high voltage differential scope.
You are confusing a few things here.

1) There is no such thing as a single ended probe for floating measurements. You always need to clip the reference / ground side of a probe somewhere in order to measure a voltage difference between two points.
2) An oscilloscope with isolated inputs is functionally comparable to using a differential probe + normal oscilloscope. Only difference is that the isolation happens inside or outside the oscilloscope
3) Needing grounding is a safety issue. If the differential probe breaks or (more likely) the user makes an error, a non-isolated oscilloscope which is floated can present dangerous voltages to the user.

So in the end the choice is between paying more for an oscilloscope with floating inputs compared to using an external isolation device like a differential probe combined with an oscilloscope. What is most economic and desirable, depends on the requirements. Handheld oscilloscopes with isolated inputs typically have less features as they are more geared towards simple field measurements.
« Last Edit: December 12, 2023, 07:44:49 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline alm

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Re: Looking for portable oscilloscope
« Reply #36 on: December 12, 2023, 07:59:47 pm »
1) There is no such thing as a single ended probe for floating measurements. You always need to clip the reference / ground side of a probe somewhere in order to measure a voltage difference between two points.
Clipping the reference lead somewhere doesn't make the measurement any less floating, as long as the reference lead is isolated from earth. A single-ended probe is a single-ended probe (so with a signal and reference lead with an imbalanced impedance to ground) that is specifically designed for floating measurements like the HCK/Staubli IsoProbe series has an isolated BNC connector and a reference lead that is much better insulated than your average probe designed for grounded scopes.

3) Needing grounding is a safety issue. If the differential probe breaks or (more likely) the user makes an error, a non-isolated oscilloscope which is floated can present dangerous voltages to the user.
Needing ground is a safety issue for scopes with non-isolated inputs. So there is a distinct advantage here for scopes with isolated inputs in places where grounding is difficult.

I do agree that scopes with isolated inputs are more expensive and more limited in features. I wouldn't want one as my primary bench scope, but it sounded like this application doesn't need a particularly advanced scope.
 
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Offline rhb

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Re: Looking for portable oscilloscope
« Reply #37 on: December 12, 2023, 08:42:46 pm »
I have an HDS272S which I'd ordinarily recommend, however as you mention 3 phase, a Hanmatek DOS1104 *might* be  what you want.  Internally it's an Owon SDS 1104 but without the deep memory chip or the mains supply.  I runs on 5 V in.  I ordered one from Aliexpress along with a couple of 10 A-hr LiPo cells.  The BMS/boost convertors came today.

With appropriate probes, the scope can float from ground and be used safely with appropriate practices.  The DOS 1104 is $206 USD.  If things go to plan I'll have a quite decent portable scope without the handheld version limitations for about $230.

I currently have a DOS 1102 and am quite impressed.  In particular, it has a good FFT which is very responsive.

I'll be starting a thread on HW hacking the Hanmateks to run on internal battery.

Have Fun!
Reg
 

Offline abgx1Topic starter

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Re: Looking for portable oscilloscope
« Reply #38 on: December 15, 2023, 09:01:00 pm »
Thank you, everybody, and sorry that I did not respond for 3 days; I had a busy week. But as I am reading your posts, I feel like it is just a bad idea to frequently measure mains voltage without differential probes + proper ground.


1. I have abandoned the idea of a handheld oscilloscope. It doesn't look safe to measure main voltage with them even with differential probes.
2. I have decided to buy Micsig differential probes.

Owon doesn't have proper grounding, so it is out of the game.
Hanmatek is not available in the EU, I need to buy it on a company VAT number. So it has to be a shop located in the EU.

So actually my shopping cart looks like this:
https://eleshop.eu/rigol-dho804-oscilloscope.html
https://eleshop.eu/dp10013-differential-probe-100-mhz-1300v.html


Any advice before making final order?
« Last Edit: December 15, 2023, 09:13:10 pm by abgx1 »
 
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Offline csuhi17

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Fnirsi oscilloscope = waste&regret
 

Offline abgx1Topic starter

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Re: Looking for portable oscilloscope
« Reply #40 on: December 18, 2023, 12:20:45 pm »
I cannot order outside of EU... I have ordered everything from local shop... 399 for the scope and 189€ for micsig probes

Sadly, rigol is out of stock everywhere, so have to wait atleast till mid january. I will let you know then :)
 

Offline csuhi17

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Re: Looking for portable oscilloscope
« Reply #41 on: December 18, 2023, 02:16:34 pm »
I cannot order outside of EU... I have ordered everything from local shop... 399 for the scope and 189€ for micsig probes

Sadly, rigol is out of stock everywhere, so have to wait atleast till mid january. I will let you know then :)
https://www.batterfly.com/shop/en/rigol-dho804?search=Dho804&description=true
Fnirsi oscilloscope = waste&regret
 
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