Looking for portable oscilloscope  - Page 1
Forum section: electronics / testgear

author: abgx1
author_rank: Contributor
timestamp: December 09, 2023, 01:36:15 pm
content: I am about to buy my first oscilloscope.It will be used for measuring on frequency inverters (mains 400V voltages up to 16kHz), mains voltages in general, and industry sensors. Additionally, I may use it for car electronics.Measurements will usually be done on-site, in not-so-easily accessible places (like industry water wells in the middle of nowhere).After some research, I've narrowed it down to 2 options:1. Rigol DHO804https://www.conrad.com/en/p/rigol-dho804-digital-70-mhz-1-25-gs-s-25-mp-12-bit-1-pc-s-2986311.html- not very portable, but can be powered from a USB-C power bank.2. Voltcraft DSO-2072Hhttps://www.conrad.com/en/p/voltcraft-dso-2072h-handheld-oscilloscope-70-mhz-2-channel-250-msa-s-8-kp-8-bit-handheld-1-pc-s-2380256.html- handheld, with its own batteries.I'm also considering these probeshttps://www.conrad.com/en/p/testec-tt-hv-250-probe-300-mhz-100-1-2500-v-107255.htmlfor both of them.Currently, I use a multimeter for these kinds of jobs, but I feel like I could find problems faster if I could see the actual waveforms.Do you think it's worth trading portability for a 'better' scope (Rigol), or should I be fine with the Voltcraft?"

author: Aldo22
author_rank: Super Contributor
timestamp: December 09, 2023, 01:51:11 pm
content: I can't tell you what you need, but I can tell you that these devices are available for less.The Voltcraft DSO-2072H is an Owon HDS272https://eleshop.de/messtechnik/oszilloskope/alle-oszilloskope/owon-hds272-handheld-oscilloscope.htmlAnd the Rigol is also available at a lower price:https://www.batronix.com/versand/oszilloskope/Rigol-DHO804.html

author: alm
author_rank: Super Contributor
timestamp: December 09, 2023, 03:08:55 pm
content: I'm not familiar with the current products on the market, but I'd definitely look for a scope that can take floating measurements at mains voltages correctly. This means if it has multiple inputs, the reference lead of all inputs should be isolated from each other, the unit should use insulated BNC jacks, and you should use probes made for floating measurements likeStäubli ISOPROBE. Both probe and scope should be rated for CAT III 600V or higher. Note that if the reference lead is at 400V, this is not attenuated by the probe, so the scope would see the whole 400V relative to ground (while the operator holding it might be grounded).

author: abgx1
author_rank: Contributor
timestamp: December 09, 2023, 03:41:13 pm
content: Thanks, I know I can buy them cheaper. I'm not going to order them from Conrad; it was just the first English website I found.Oh, I see the hassle. But that's a problem only if I measure across two phases, right?Can I avoid all the problems you mentioned if I measure only between a phase and ground?

author: alm
author_rank: Super Contributor
timestamp: December 09, 2023, 05:57:20 pm
content: With normal probes and non-insulated BNC jacks, the problem is protection against accidentally touching the reference lead (notice how I don't call it ground clip) to phase, and then touching the ring around the probe or the BNC connector, will shock you. In a mains-operated scope this is no problem because the reference lead is tied to ground, so connecting it tho phase will trip a GFCI / breaker or at least produce a spark and probably vaporize the ground lead. With a battery-powered scope you have no such protection. That's why you see the reference lead on the IsoProbe I showed is much more insulated than that of normal probes designed for grounded scopes.For a single channel, you want an insulated BNC connector on the scope and a scope that has all exposed metal (like USB connectors) and controls sufficiently isolated from the input connector. For a dual channel scope, you ideally also want the two channels to be isolated from each other, not just from the scope, so that if you clip the reference lead of channel 1 to phase, the reference lead of channel 2 won't be live.

author: abgx1
author_rank: Contributor
timestamp: December 09, 2023, 09:20:52 pm
content: Thats why I want to buy these 100:1 probes.https://www.conrad.com/en/p/testec-tt-hv-250-probe-300-mhz-100-1-2500-v-107255.htmlSo even if I accidentally touch them, there will be 2,3V instead of 230V...Is that a bad idea?

author: alm
author_rank: Super Contributor
timestamp: December 09, 2023, 09:46:58 pm
content: Quote from: abgx1 on December 09, 2023, 09:20:52 pmOnly if you connect the tip to phase and then touch the center pin of the BNC connector. But if you connect the reference ('ground') lead to phase and touch for example the ring close to the probe tip, or anything on the scope that is connected to this reference lead (like any connector on a non-isolated scope), there will be 230V on that. The 1:100 attenuation is only for the tip. The same applies to true isolated probes like the one I showed, but those probes are designed in a way that when used with scopes with isolated inputs, the reference lead is well insulated from the user.I'd say probes like this are not safe for battery powered scopes. Only probes where both the tip and reference lead are fully insulated from the user are safe for making measurements beyond separated extra low voltage (< 50V RMS from a source isolated from mains). Note the note in theprobe datasheet(emphasis as in datasheet):Quote

author: Fungus
author_rank: Super Contributor
timestamp: December 09, 2023, 10:15:25 pm
content: Quote from: abgx1 on December 09, 2023, 09:20:52 pmPossibly.Imagine you connect the ground clip of a probe to the live phase wire.All the exposed BNC connectors on the scope are now live...A 100x probe is a good idea but it's not a guarantee.Edit: FWIW the DHO800 comes with little rubber caps so you can do this:

author: csuhi17
author_rank: Frequent Contributor
timestamp: December 09, 2023, 11:53:32 pm
content: Quote from: Fungus link=topic=404805.msg5213088#msg5213088 .date=1702160125the "ground" point of the calibration signal is connected to the reference "ground" point of the four channels.It would also be worthwhile to put a cap on it.

author: smaultre
author_rank: Regular Contributor
timestamp: December 10, 2023, 06:49:13 am
content: You can see Fluke 199 series or Agilent U1620.. Isolated inputs are not low-cost thing.

author: tggzzz
author_rank: Super Contributor
timestamp: December 10, 2023, 09:00:02 am
content: Quote from: abgx1 on December 09, 2023, 01:36:15 pmYou would benefit from reading and understanding the Tektronix references athttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/especially the safety references.TL;DR isnever float a scope. There are many subtle ways it could damage the UUT, and/or the scope, and/or you.A few scopes are explicitly designed to be used (relatively) safely in cases such as you describe, typically with isolated inputs.Make sure any probe's AC voltage-vs-frequency rating is not exceeded. If the probe doesn't have that specified, don't use it.

author: Fungus
author_rank: Super Contributor
timestamp: December 10, 2023, 10:55:56 am
content: To be honest: For looking at basic 16kHz signals in outdoor conditions I'd be tempted to go for a single channel handheld. You don't need deep memory, serial decoders, video triggers, etc. for that.Something like that Voltcraft/Owon shown in the first video would do it. Look for one that can be charged with a USB powerbank.Maybe even this combined with a decent probe and a voltstick to check which is the live wire and which is neutral/GND:

author: adam4521
author_rank: Regular Contributor
timestamp: December 10, 2023, 11:37:59 am
content: Middle of nowhere, wells, water, 400V, inverter, it’s like a cacophony of jangling alarm bells. In most contexts this would be super-regulated industrial work. They’d start with whether you need to do the test in situ at all, then would follow detailed risk assessment, method statement, two people at least etc. Eventually, a comparatively low price/performance, but very regulated, isolated, tested device from premium supplier like Fluke might be suitable for the test activity, within a procedure that is entirely written out in advance. Dave has done videos on why those types of device exist and are expensive compared to the hobbyist devices.

author: alm
author_rank: Super Contributor
timestamp: December 10, 2023, 11:47:02 am
content: I'd definitely look for a CAT III rated device designed for floating measurements with properly isolated or insulated (for single channel) connections, and not like the Voltcraft in the first post: "please don't touch the connectors while the scope is connected to a voltage source".

author: abgx1
author_rank: Contributor
timestamp: December 10, 2023, 12:29:58 pm
content: It's getting way more complicated and expensive than I thought.I think that intentional floating measurement is out of the game for now. If I understand correctly, the only problem I need to solve now is when I accidentally connect the ground to the mains voltage (which can easily happen).Now I see that I need to gain a lot more knowledge about scopes. I've read some articles and watched some videos, etc. [Here's a link].But, what if I buy a scope operated from main voltage? In that case, the ground point will always be connected to the ground in the outlet. So, the worst-case scenario is a short circuit between the scope ground and mains voltage, which is not ideal but much safer than the risk of being electrocuted.Or should I abandon the idea of buying a scope completely until I'm ready to pay 3-4k€ for the Fluke?

author: csuhi17
author_rank: Frequent Contributor
timestamp: December 10, 2023, 01:03:12 pm
content: Wouldn't any oscilloscope and differential probe solve his problem?

author: Fungus
author_rank: Super Contributor
timestamp: December 10, 2023, 01:41:15 pm
content: Quote from: abgx1 on December 10, 2023, 12:29:58 pmAny 'scope can be grounded. The Rigol DHO800 has a grounding connector and comes with a big green/yellow wire in the box.Me? I say "safety" is as much about procedure as the hardware. You can kill yourself just as dead with a $4000 Fluke as with a cheapo Chinese meter.a) Wear gloves (and eye/hearing protection for very high power circuits)b) Don't trust your life to the color of wires. Make sure you know which is the live wire and whether the neutral wire is grounded or not. You need a low-Z multimeter for this. I'd get a Fluke 113 if my job was based around "mains AC" (for it's price, high CAT rating and sheer idiot-proofness).c) Don't do it alone, have somebody else around whenever possible.d) ...now you're ready to start the test procedure.Quote from: adam4521 on December 10, 2023, 11:37:59 amIt sorta depends on the power of the inverter. A properly-fused 5A inverter isn't as scary as a 1kA inverter...

author: abgx1
author_rank: Contributor
timestamp: December 11, 2023, 04:33:55 pm
content: Well, at some point, the amperage of the fuse doesn't matter anymore because it just won't trip, no matter how hard you're trying. 🙂 The frequency inverters I commonly come across are in the range of 0.18-11 kW, which means around 25-26A at max.Anyway, I did some studying, and I see four options:1. Buying differential probes - That's too expensive, at least for now.2. Buying a scope with isolated inputs - That's even more expensive.3. Using a grounding connector with a big green/yellow wire connected to the 100% safe grounding point (for example, a lightning rod on those wells) as a reference point so I do not have to use the probe grounding lead at all - That sounds pretty safe to me.4. Could I use the second channel as a reference point? I mean, I would connect channel 1 through a 1:100 probe on mains voltage. Then I would connect channel 2 through a 1:100 probe to the ground. Finally, I would subtract channel 2 from channel 1.Now, when I see it written, I think that option 4 is impossible since I will not be able to measure any voltage on channel 1 without grounding. Is that true?Currently, I am leaning toward the Rigol DHO804 and option (if option 4 is not possible), if you guys do not have a better idea that does not cost a four-figure price. I have excluded Owon from selection since it doesn't have a grounding point other than one on the probe..

author: Fungus
author_rank: Super Contributor
timestamp: December 11, 2023, 04:39:02 pm
content: Quote from: abgx1 on December 11, 2023, 04:33:55 pmNo need.The DHO800 comes with a big yellow/green ground wire in the box. You can ground the scope then just probe the mains with a single probe on channel 1.

author: shapirus
author_rank: Super Contributor
timestamp: December 11, 2023, 04:41:37 pm
content: Quote from: abgx1 on December 11, 2023, 04:33:55 pmIf we consider it from the purely mathematical point of view, since one channel's value is subtracted from another, and they both have the same reference point, the referent point cancels out and does not matter anymore, meaning the probe ground clips aren't even required in this case.Practical implementation is a different story. I can't confirm that it works, but something tells me that it should be viable.p.s. you can still touch the exposed ground metal parts on the probes, if they have them. That requires extra care.

author: csuhi17
author_rank: Frequent Contributor
timestamp: December 11, 2023, 06:26:13 pm
content: Quote from: abgx1 on December 11, 2023, 04:33:55 pmIf I wrote something wrong or ambiguous, please correct me, unfortunately English is not my first language.If it is enough for you to just see the signal and not perform any serious measurements on it, and the display size is fine for you:Differential measuring head:Hantek HT8050 for about 180 Euros or Micsig for about250 EurosBangood sell it cheaper 150USD.Small handheld scopeHDS242 around 140 Euros.The 40Mhz configuration comes out to around 320 Euros.You wrote that ~16 kHz should be around.If you need a more serious one, the oscilloscope is at least the Rigol DHO804 or maybe the others can recommend a cheap portable version.Forget Fnirsi and company.Maybe the DPOX180H, but only if you can get it cheap.it is worth putting a cap on each channel, and covering the measuring points of the 1kHz test signal with some sort of insulator.If I understand correctly what you wrote in point 4.You will not be able to use the two channels in such a way that the "Ground" wire of both channels is not connected anywhere. and You connect the "signal" wire of the first channel to the main voltage and the "signal" wire of the second channel to ground.This is wrong in principle, since the "Ground" reference point of both channels is "floating?"Did you read about the differential probe when you came up with this?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.

author: abgx1
author_rank: Contributor
timestamp: December 11, 2023, 08:32:13 pm
content: cushi, you understand point 4 correctly.I wasn't reading about a differential probe, it was just a random idea that I got. But now I understand that it is not possible to measure completely without ground when not using differential probe.So I will stick with option 3 + Rigol 804 and maybe later I will buy some differential probe...

author: csuhi17
author_rank: Frequent Contributor
timestamp: December 11, 2023, 09:01:00 pm
content: okWhen I measure higher voltages, I always use one of the battery scopes, floating.I don't know how to measure with a grounded oscilloscope!check properly how to do it, so that there is no problem.

author: shapirus
author_rank: Super Contributor
timestamp: December 11, 2023, 09:09:20 pm
content: Quote from: shapirus on December 11, 2023, 04:41:37 pmSo 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.

author: smaultre
author_rank: Regular Contributor
timestamp: December 12, 2023, 08:59:42 am
content: I'm just trying the same trick ch.A - ch.B with Fluke. I't works fine, math is GREEN line.

author: abgx1
author_rank: Contributor
timestamp: December 12, 2023, 10:15:38 am
content: 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...

author: 2N3055
author_rank: Super Contributor
timestamp: December 12, 2023, 12:17:37 pm
content: Quote from: csuhi17 on December 11, 2023, 06:26:13 pmFluke 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..

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 12, 2023, 12:19:18 pm
content: The Micsig tablets scopes are also well worth a look.

author: nctnico
author_rank: Super Contributor
timestamp: December 12, 2023, 12:22:07 pm
content: Quote from: mikeselectricstuff on December 12, 2023, 12:19:18 pmI 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.

author: 2N3055
author_rank: Super Contributor
timestamp: December 12, 2023, 12:24:43 pm
content: Quote from: mikeselectricstuff on December 12, 2023, 12:19:18 pmThey used to have an isolated handhelds before but not anymore.

author: abgx1
author_rank: Contributor
timestamp: December 12, 2023, 01:50:57 pm
content: What is the cheapes differential probe which can be used on main voltage?

author: nctnico
author_rank: Super Contributor
timestamp: December 12, 2023, 02:05:44 pm
content: Quote from: abgx1 on December 12, 2023, 01:50:57 pmLast time I checked the CAT rated ones from Micsig are the most economic ones.

author: shapirus
author_rank: Super Contributor
timestamp: December 12, 2023, 02:08:21 pm
content: I believe there also were some feasible DIY designs discussed on this forum (that someone actually implemented). Search should show them.

author: Fungus
author_rank: Super Contributor
timestamp: December 12, 2023, 04:34:56 pm
content: Quote from: abgx1 on December 12, 2023, 01:50:57 pmMicsig.

author: alm
author_rank: Super Contributor
timestamp: December 12, 2023, 07:32:07 pm
content: Quote from: shapirus on December 11, 2023, 09:09:20 pmThe 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.Quote from: nctnico on December 12, 2023, 12:22:07 pmNo, 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.

author: nctnico
author_rank: Super Contributor
timestamp: December 12, 2023, 07:40:32 pm
content: Quote from: alm on December 12, 2023, 07:32:07 pmYou 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 oscilloscope3) 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.

author: alm
author_rank: Super Contributor
timestamp: December 12, 2023, 07:59:47 pm
content: Quote from: nctnico on December 12, 2023, 07:40:32 pmClipping 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 pmNeeding 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.

author: rhb
author_rank: Super Contributor
timestamp: December 12, 2023, 08:42:46 pm
content: 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

author: abgx1
author_rank: Contributor
timestamp: December 15, 2023, 09:01:00 pm
content: 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.htmlhttps://eleshop.eu/dp10013-differential-probe-100-mhz-1300v.htmlAny advice before making final order?

author: csuhi17
author_rank: Frequent Contributor
timestamp: December 15, 2023, 09:41:19 pm
content: 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=searchyou won't get it this year, but I think it's much cheaper.

author: abgx1
author_rank: Contributor
timestamp: December 18, 2023, 12:20:45 pm
content: I cannot order outside of EU... I have ordered everything from local shop... 399 for the scope and 189€ for micsig probesSadly, rigol is out of stock everywhere, so have to wait atleast till mid january. I will let you know then

author: csuhi17
author_rank: Frequent Contributor
timestamp: December 18, 2023, 02:16:34 pm
content: Quote from: abgx1 on December 18, 2023, 12:20:45 pmhttps://www.batterfly.com/shop/en/rigol-dho804?search=Dho804&description=true

author: aae30
author_rank: Contributor
timestamp: August 28, 2025, 02:05:45 pm
content: Quote from: rhb on December 12, 2023, 08:42:46 pmDid you ever get around to doing this? Took a look inside, and looks to me like it might berelatively simple to do w/o (m)any custom parts.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: August 28, 2025, 02:49:30 pm
content: OWON HDS160I did advise it to friend who work for solar panels \ inverters on a field for some basic troubleshooting. From his word: It appears extremely useful to use the same probe for scope and voltage metering , switching back and forward scope to DMM by single button. ... you basically holding same point and switching .. Scope are OK up to 200 -300K freq , exact max for inverters. it has 1:500V Div. for scope He had a case it swallow 1200 V P-P .if you forgot to recharge - just replace one 18650on negative side a bit small screen for scope , and some homemade shade screen to off direct light . it quite light to carry . so after a few month all his crew got the samebefore i gave him my OWON HDS241the response was .. to much cables to deal it on roof, sometime it get lost ... a bit expensive to replace if it fall from roof accidently .. so that HDS160 ( 120 - 20000 counts) almost idealand 60000 - nice wide range ... switch to 600 still have 0.1 resolution

author: norbert.kiszka
author_rank: Frequent Contributor
timestamp: August 28, 2025, 03:33:55 pm
content: Rigol DHO800 and DHO900 series are powered from USB-C PSU or power bank. But there is one thing that most of the electronic/electrical engineers/technicians will like to not think of or just forget to think of.There is something called as aearthing systems, which IMHO is not a fully proper name, because also applies to simplest devices powered from a single 1.5 V battery and fully enclosed. This is a just a surface of a safety knowledge of a safety in electrical devices. I think, most of people here, didn't spend hours on state exams about safety related to any electrical work.Extra low voltage (ELV) PSU's like USB ones, creates another earthing system. Which is one of three: SELV, PELV and FELV. USB power supplies usually are SELV, at least in theory. In practice those are often between SELV and FELV, which means this is a huge safety hazard, especially if there is a tiny amount of moisture in the air. 70% air humidity can be a death trap - I know something about it from my personal experience.Working with the oscilloscope and power grid it's not just simple as just buy first better probe or make it by Yourself. When scope is powered from a power supply that claims to be SELV, You either need to have fully secured PE-GND connection or to be absolutely sure about Your equipment and what are You doing. Bananas plugs with thin and Chinese made "copper", are very far from that.Rigol supplied many of those scopes with a PSU's which are death traps. I bought DHO924S which was supplied with a Lite-On USB-C PSU. I tested it with a insulation tester (fancy ohm meter with higher voltage) and it failed pretty quickly. After I tear it down, reason was pretty obvious - it was designed to be very cheap, without safety in mind.I heard in last couple month Rigol switched those two previous PSUs to a Delta brand. From my experience Delta makes very reliable and very safe power supplies and other things. But You never know if this is a genuine one or some fake.Used insulation testers (another name: Riso meter) are very cheap. You can get one for like 80$, which can save Your or somebody else life. Not speaking of health, because burns and paralysis are not fun.