A digital scope for audio circuits, what do i need?

[MrSadman]

I think that right now the choice is between Rigol and Hameg. Agilent is out of my pricerange, unless I go for the 2000 series but to get the same functionality I'd have to spring for the 3000 series, Tek don't have anything nice in the entrylevel market, GW Instek GDS2000 has some downsides pointed out by Dave.

Other scopes I could get are Tenma(something rebranded by Farnell I think), Lecroy, Uni-T(Again rebranded scopes I think)

Now, I could just go with the Rigol and be done with it, but I am a bit concerned about aftersales suport, should something happen to it. Infact, this is the only reason I am actually considering spending some more money and getting an Agilent, because I know they have a really good service policy here. Also, I understand all the upgrades are software implemented so i could just buy them if the need arises later on? Think it's the same with Rigol?

The Hameg scopes are something I haven't had a chance to really look at, but the basic numbers seem promising.

[Paul Price]

Rigol Scopes!

Rigol websites  do not allow you to register yourself so as to login. It doesn't accept  your registration, says it has sent you an email which is never sent.

Rigol websites does not post any scope firmware updates to firmware, does not even mention anything about updates, and  even though they are available, you have to call tech support and beg to get one that is undocumented as to fixes,  nor is any tech support available except by email on the website. You can contact them by phone and they were honestly trying to be helpful from that way of communication. Only tech support info on website is a list of discontinued scope models.

I requested a firmware update, hoping it would solve some scope problems, but got first an update for their DG waveform generator, then after calling again, got a DS4000 series firmware update with incorrect instructions on how to enter the firmware update mode, I had to discover how to do this myself. The firmware did not solve my use problems with the scope, fixed somethings unknown and made some other situations of use more difficult than the original firmware.

Agilent, on the other hand called me back about questions before purchase and a service engineer talked with me for almost an hour in a phone call abut their scopes, even offered to bring any model by for a test drive. Same experience with Tektronix

Never the less, I didn't send the scope back for a refund because for the very high memory and the price it still was the best economical solution for me, even though this scope has a fair share of anomalous behaviors, especially with slower sweep speed displays, trying to capture a single-sweep, quirky way of shifting triggering modes, some very slow sweep settings are unusable and to save a single 70-mega sample CSV waveform image data to a USB stick takes over 2 and 1/2 hours that locks up the scope from being used for any other purpose...and this is a $3000 US priced model, not a cheaper hobbyist model.

[marmad]

Rigol websites  do not allow you to register yourself so as to login. It doesn't accept  your registration, says it has sent you an email which is never sent.

I haven't had any problems registering at the Rigol site in order to download documents.

Rigol websites does not post any scope firmware updates to firmware, does not even mention anything about updates, and  even though they are available, you have to call tech support and beg to get one that is undocumented as to fixes,  nor is any tech support available except by email on the website. You can contact them by phone and they were honestly trying to be helpful from that way of communication.

Unfortunately, it's been well-known for awhile that Rigol does not distribute FW very well via the normal internet channels. OTOH, I haven't had a bit of trouble getting the latest FW - or reporting bugs to Rigol - via my dealer, the one who sold me the DSO. Why wouldn't you contact your dealer about FW upgrades?

...especially with slower sweep speed displays, trying to capture a single-sweep, quirky way of shifting triggering modes, some very slow sweep settings are unusable...

As reported elsewhere, this 'quirky' behavior has to do with the way the Rigol handles intensity grading/persistence. At <= 100ms/div, the Rigol is capturing full screens of data so that they can be combined into the intensity/persistence map (impossible to do when 'rolling'). Whether you like this behavior or not is a question of preference, but there's nothing especially strange about it.

...and to save a single 70-mega sample CSV waveform image data to a USB stick takes over 2 and 1/2 hours that locks up the scope from being used for any other purpose...

I think something must be wrong with your scope. It takes me 4.25 minutes to save a 14MPt CSV file on the DS2000 - 5x that would be 21.25 minutes. BTW, if I had the desire to save 70MPt CSV files often, I would just write a small utility to convert the sample data to ASCII CSV format myself at the PC - which is fairly simple - and would save oodles of time later.

[Paul Price]

Marmed:  I have repeatedly, over several efforts over several weeks attempted to get a log in registration. Always fails.

Has anyone on eevblog  managed to get a log in registration on their website?

If so, did it logging in give you any other information about their scopes?

Rigol does not following  the convention of posting updates, so the effect is to make the a firmware download a secret and difficult.  That is not tech support, that is simply red tape.

I contacted Rigol engineer about the USB problem and they said that slow USB save was normal.
A friend of mine who bought the same scope wrote an email about the same problem to a Rigol design enginee. The engineer  who wrote back said below about the slow USB save:
-------------------------------------------------------------------------

thanks for your email.
 
You are right. But our previous idea of product definition is that mainly
function of scope is analysis instead of data transfer, speed etc..
 
of course, if it can support fast speed, that is the best.
 
So far, I don't know if we release similar product with USB3.0 interface.
 
 
Mit freundlichen Grüßen/With best regards
 
James Zhu
Rigol Technologies EU GmbH
Lindberghstraße 4
82178 Puchheim
+49 (0)89 - 8941895-21
Cell:+491752239450
E-Mail: zhuguangyuan@rigol.com
Skype:  zhuguangyuan78
------------------------------------------------------------------------------------------------

I requested videos of scope operation from Tektronix and Agilent, which they promptly sent. The Agilent scope at about the same level of price showed much better display update performance and roll range. The Rigol surprises me with display updates that are history and jump back and forth at speeds between 100mS/div and 5mS div, with the effect less noticeable towards the fastest sweep rates.

[marmad]

Rigol does not following  the convention of posting updates, so the effect is to make the a firmware download a secret and difficult.

Again, I'm not sure why you don't just contact your dealer for new FW? My dealer in the Czech Republic will always get the latest FW to me.

I contacted Rigol engineer about the USB problem and they said that slow USB save was normal.

2.5 hours is not normal - unless you were joking (I quoted my speeds to you). Every DSO I've tried has been using low-speed USB, so they've allways been a bit slow - but nothing like 2.5 hours for ~800MB (the CSV files are approximately 11 * sample length).

I requested videos of scope operation from Tektronix and Agilent, which they promptly sent. The Agilent scope at about the same level of price showed much better display update performance and roll range. The Rigol surprises me with display updates that are history and jump back and forth at speeds between 100mS/div and 5mS div, with the effect less noticeable towards the fastest sweep rates.

I can't attest to exactly how those DSOs are handling low time base settings, but slow time bases mean slow display updating on every DSO. The Rigol has 14 divisions, so that means for example,  that @100ms/div, it will do one screen update every ~1.4 seconds - while the Agilent 2000 X-Series (with 10 divs) will do one screen update every ~1 second.

[Paul Price]

I was not joking about the 2.5 hours to save a 700mega point CSV file to a USB 2.0 memory stick.

[marmad]

I was not joking about the 2.5 hours to save a 700mega point CSV file to a USB 2.0 memory stick.

Ok - I will test myself with 56MPts CSV file right now (4/5ths the size of your file) and post the speed.

[marmad]

I was not joking about the 2.5 hours to save a 700mega point CSV file to a USB 2.0 memory stick.

Yes, I see what you mean - trying to save massive CSV files to USB stick is unusably slow. When  I reached 1 hour while trying to save 56MPts as CSV, I broke out of the routine.

Well, I'm working on a new version of my RUU software with enhanced file capabilities (since they fixed the transferring bugs in the newest DS2000 FW). It works with DS4000s - and the next version will allow you to create and save CSV files from the PC using the raw sample data transferred from the DSO, so it will be MUCH faster for getting big CSV files of the waveform. I hope to have it ready in the next couple of weeks.

[MrSadman]

Well, it seems i have my choice narrowed down to Rigol D2000 series, Hameg HMO series or Agilent 3000
Rigol:
+
by far the best bang for the buck, doesn't seem to be lacking in any area
-
Doesn't have a local retailer and thus, no local suport.
Agilent:
+
Everything is upgradeable, so I could go for a lower spec model for now and upgrade as needed.
Performacwe wise should be similar to the Rigol
-
Cost, even without the upgrades
Hameg:
Somewhere between the Rigol and Agilent in almost all aspects, but has a low waveforms per second figure. Watching the review videos on youtube didn't leave me as impressed as the Rigol review by Dave

if you can add something to this list to help me decide, please do so.

[marmad]

Rigol:
-
Doesn't have a local retailer and thus, no local suport.

I live in NL and bought my Rigol from EEVBlog member Drieg - his real name is Petr Šmíd (smidp321@gmail.com) - and he runs Silcon Electronics in the Czech Republic (and is the Rigol distributor there). That's almost as far away from me as it is from you  But he's really a great person - and he may be able to offer you a good deal. He also has fantastic after-sales support.

Agilent:
+
Everything is upgradeable, so I could go for a lower spec model for now and upgrade as needed.

Yeah, but the price of those upgrades is pretty steep. BTW, did you know people are starting to hack the Rigol?

[MrSadman]

Something that just occurred to me. Modern scopes require proper wiring, mainly a PE connection. This is something that I don't have. I guess that sort of limits my choices to the Fluke scopemeters or an USB scope....

[ddavidebor]

No, to the scopemeter only.

Even for pc scope is required, or your entire pc will become at an hight voltage.


In my opinion is better to spend money to do the pe instead of buy a scope
Safety first

[Paul Price]

If a PE connection means having a three wire ground system, you don't need to stress yourself about that.
You don't need a PE connection to use an oscilloscope no more than you would using a radio or a PC on anything else in your house that plugs in. And if you did have a PE, you just don't connect an oscilloscope probe ground directly to any AC mains circuit. If you did connect your scope with a PE connection, you would damage the oscilloscope probe, likely your oscilloscope also, and you could possibly electrocute yourself if you touched the circuit and the oscilloscope ground connection at the same time while trying to connect the scope to a live AC circuit.

[marmad]

You don't need a PE connection to use an oscilloscope no more than you would using a radio or a PC on anything else in your house that plugs in.

You absolutely do for DSOs. It's dangerous in a couple ways if you don't.
From a Tektronix document on the subject:

“Floating” a ground referenced oscilloscope is the technique of defeating the oscilloscope’s protective grounding system – disconnecting “signal common” from earth, either by defeating the grounding system or using an isolation transformer. This allows accessible parts of the instrument such as chassis, cabinet, and connectors to assume the potential of the probe ground lead connection point. This is dangerous, not only from the standpoint of elevated voltages present on the oscilloscope (a shock hazard to the operator), but also due to cumulative stresses on the oscilloscope’s power transformer insulation. This stress may not cause immediate failure, but may lead to future dangerous failures (a shock and fire hazard), even after returning the oscilloscope to properly grounded operation! Not only is floating a ground-referenced oscilloscope dangerous, but the measurements are often inaccurate. This results from the total capacitance of the oscilloscope chassis being directly connected to the circuit under test at the point where the common lead is connected. At higher frequencies, severing the ground may not even break the ground loop as the line-powered instrument exhibits a large parasitic capacitance when floated above earth ground.' Etc.

[alm]

If a PE connection means having a three wire ground system, you don't need to stress yourself about that.
You don't need a PE connection to use an oscilloscope no more than you would using a radio or a PC on anything else in your house that plugs in. And if you did have a PE, you just don't connect an oscilloscope probe ground directly to any AC mains circuit. If you did connect your scope with a PE connection, you would damage the oscilloscope probe, likely your oscilloscope also, and you could possibly electrocute yourself if you touched the circuit and the oscilloscope ground connection at the same time while trying to connect the scope to a live AC circuit.

IEC recognizes (among others) class I and class II protection classes for appliances. Class II requires double insulation (eg. larger clearance/creapage) to make it extremely unlikely that a single fault will bring the user into contact with mains. Class I does not require this, because any conductive surfaces (like the metal case) is connected to PE, and shorting mains to PE should either trip the GFCI or (if it's a dead short) blow the fuse. At no point will the case become elevated to dangerous potentials above PE. If you remove the PE connection, a single loose wire touching the case can elevate it to mains potential. Unless the floor or your shoes/chair are a very good insulator, this will result in you acting as a current carrying conductor. So no, a PC or radio with three-prong plug without PE is not safe. Just because most countries consider it too expensive to go around and rewire all old buildings does not make it safe.

A scope is even worse. You don't generally connect your radio to random circuits, but you do clip your scope to unknown DUTs that may have faults. For example, some old Fluke bench DMMs with battery option carry mains all the way to the charging circuit. The unknown DUT (not grounded either) may also have a loose wire touching against the chassis. You can easily accidentally clip the ground lead to this. People make mistakes, and sometimes this mistake destroys a piece of equipment like a scope probe. Getting electrocuted because of a mistake is quite harsh, however.

[Paul Price]

In many countries of Europe three wire AC plugs are not used at all, and people use oscilloscopes and every other type of appliances form PC's to vacuum cleaners to any other imaginable type of devices all the time. Instead of PE connections GFI Ground Fault Interrupters are used for safety and work very well. 

I repeat: It is deadly dangerous to ground an oscilloscope to an earth ground, both for you and the scope.  If you touch a live AC mains circuit and the scope with another part of your body you will suffer a serious shock that would likely not occur if a two wire connection was used.

Whenever using a scope or a refrigerator, it must be used with caution if you think you might connect somehow directly to the AC mains.
In all situations, this means don't work on equipment barefoot on a wet cement floor, don't use the scope in the shower or swimming pool, you don't play with an oscilloscope outside in the rain. Don't work on electrical equipment with wet clothes or shoes. Don't sit on metal benches or chairs while working on equipment or high voltages,  don't work on any electronic equipment naked or barefoot. Always try a single hand, a one-handed approach when working with mains connected equipment or with any high voltages. Above all, don't ground yourself to a PE connected piece of equipment with one hand and touch any other equipment with the other you are not sure about.

This is just common sense.

Secondly, ground loops between PE connected grounds can damage the circuit you are working on or cause you to experience mild shocks.  Even though PE connected devices should eliminate this problem, difference in ground resistance and generated currents from separate AC mains outlets connected equipment, even in the same room can create small voltage, but high-AC current connections. These low voltages with high  currents can blow out USB and printers etc, and you might even a low-voltage spark when connecting these grounds.

Connecting yourself between PE grounded equipment and equipment with faults or AC mains circuits might give you possibly fatal shocks that would not happened if the test equipment you are using ware using two wire AC connections and (and it helps if you have it) GFI.

If there is any suspicion that a piece of equipment could be damaged and presenting an AD mains hazard, this can be quickly checked with an AC handheld voltmeter. If you are getting high voltage readings to an earth ground, you should not connect your scope to it until you've repaired the trouble.

In most instances, these types of AC mains faults do not exist, to be sure you can always check with a multimeter before you risk connecting yourself to any equipment with your hands.

When repairmen work on high-voltage main lines, they deliberately isolate themselves and any other metal around them from an earth ground, or else they could be killed.  How do you think it is possible for repair technicians to work on 500000 VAC lines if they didn't isolate themselves completely from AC grounds.

[Harvs]

In many countries of Europe three wire AC plugs are not used at all, and people use oscilloscopes and every other type of appliances form PC's to vacuum cleaners to any other imaginable type of devices all the time. Instead of PE connections GFI Ground Fault Interrupters are used for safety and work very well. 

I'm not sure if we're talking about the same thing, but we've just been through ground disconnection in another thread.
https://www.eevblog.com/forum/testgear/first-impressions-and-review-of-the-rigol-ds2072-ds2000-series-dso/1230/

The reality is, if you don't have a ground connection on the DS2000, you will have half the mains potential on the BNC grounds.

Are you talking about something else?

[marmad]

I repeat: It is deadly dangerous to ground an oscilloscope to an earth ground, both for you and the scope.  If you touch a live AC mains circuit and the scope with another part of your body you will suffer a serious shock that would not occur if a two wire connection was used.

Sorry, I'll take the expertise and recommendations of companies that have been building oscilloscopes for decades.

BTW, most DSOs have switched-mode power supplies, which means noise reduction caps between the mains and ground - so if you power up your DS4000 without a ground connection, you will have 110-120VACrms on the chassis and BNC jacks.

Someone just posted over in the Rigol thread about getting a shock when they were running the DS2000 without a ground connection.

[ddavidebor]

In many countries of Europe three wire AC plugs are not used at all, and people use oscilloscopes and every other type of appliances form PC's to vacuum cleaners to any other imaginable type of devices all the time. Instead of PE connections GFI Ground Fault Interrupters are used for safety and work very well. 

I'm not sure if we're talking about the same thing, but we've just been through ground disconnection in another thread.
https://www.eevblog.com/forum/testgear/first-impressions-and-review-of-the-rigol-ds2072-ds2000-series-dso/1230/

The reality is, if you don't have a ground connection on the DS2000, you will have half the mains potential on the BNC grounds.

Are you talking about something else?

Well, more dangerous is that if you probe a 14.000v crt power line with the ground clip, all the damn piece of metal of your scope will become 14000v

[ddavidebor]

Ah and paul, please shut up.

It's a public forum, full of engineer and full of idiots and morons.

Leave the natural selection to darwin.

Some idiot can kill themself reading you.

[c4757p]

14.000v crt power line

This is why I never use delimiters inside a number like that! It took me a second to process what CRT would run on 14V and require five-digit precision!

[MrSadman]

Probably going to go for a USB scope and use it with a laptop. I know the proper choice would be to fix the wiring problems but I can't do this safely and will be moving once I finish school anyway.

[marmad]

In many countries of Europe three wire AC plugs are not used at all, and people use oscilloscopes and every other type of appliances form PC's to vacuum cleaners to any other imaginable type of devices all the time.

BTW, PC's use switched-mode supplies as well - and will also have 90-120VAC present on the metal case if you hook them up without a ground wire. I found that out the hard way when the ground line connecting my PC became accidentally disconnected once.

Probably going to go for a USB scope and use it with a laptop. I know the proper choice would be to fix the wiring problems but I can't do this safely and will be moving once I finish school anyway.

Another alternative is a battery-powered DSO or handheld. They can usually safely measure 30V to 600V - depending on whether they're double-insulated.

[alm]

Battery powered scopes without isolated channels, especially those with metal BNC connectors, scare me. If I'm going to clip probes to a DUT involving mains, then I want any exposed metal connected to these probes solidly bonded to earth, since I'm likely connected to earth somehow.

I fail to see how using a PC-based scope connected to a laptop improves safety: apart from the BNC connectors and USB connectors on the scope, the connectors on the laptop will also become live when clipping the ground lead to the wrong circuit node. Keep in mind that features, bang per buck and usability of USB scopes is usually way inferior to bench scopes.

Note also that if you're into low power stuff, eg. an Arduino powered from a USB connector, a bench power supply, or a small plug pack, then it's quite hard to receive a shock from it, and I wouldn't be too worried about grounding a scope. It's good practice to ensure a good ground connection, and I would consider it critical when working on anything involving high energy circuits like mains, but it's not like a 5 V / 500 mA USB supply is going to electrocute you. Of course if the case is connected (via caps) to mains, like apparently on the Rigol DS2000 series, then it's a good idea to have a ground connection. The caps should be small enough so the shock is not dangerous (otherwise Rigol screwed up), but some electronics can get unhappy when receiving 120 V on their inputs.

[Harvs]

Of course if the case is connected (via caps) to mains, like apparently on the Rigol DS2000 series, then it's a good idea to have a ground connection. The caps should be small enough so the shock is not dangerous (otherwise Rigol screwed up), but some electronics can get unhappy when receiving 120 V on their inputs.

Just checked the DS1000 and it's the same as well.  DS2000 has 4.7nf from L-G and N-G, the DS1000 has 2.0nf.  My PC psu has 10nf.