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Looking for portable oscilloscope

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nctnico:

--- Quote from: alm on December 12, 2023, 07:32:07 pm ---
--- Quote from: nctnico on December 12, 2023, 12:22:07 pm ---For measuring high voltages / mains safely, you'd need a CAT rated differential probe though.

--- End quote ---
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.

--- End quote ---
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.

alm:

--- Quote from: nctnico on December 12, 2023, 07:40:32 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.

--- End quote ---
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.


--- Quote from: nctnico on December 12, 2023, 07:40:32 pm ---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.

--- End quote ---
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.

rhb:
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

abgx1:
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?

csuhi17:
https://www.banggood.com/hu/Micsig-Oscilloscope-1300V-100MHz-High-Voltage-Differential-Probe-Kit-3_5ns-Rise-Time-50X-or-500X-Attenuation-Rate-DP10013-p-1987592.html?cur_warehouse=CN&rmmds=search

you won't get it this year, but I think it's much cheaper.

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