Purchasing first oscilloscope for serious research/commercial electronics work - Page 1
Forum section: electronics / testgear

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 09:07:31 am
content: Hi all,I'm an Australian computer science student/researcher whose academic and personal (commercial) work is starting to move into the electronics space. I have no understanding of electronics, so I recently started diving into the subject and studying. I am going to be doing a lot of typical electronics work, including a lot of embedded systems work, but I will also be doing a lot of optics and photonics work. For this purpose, and since some websites (au.element14.com) have Black Friday discounts, I want to look into purchasing an oscilloscope now.I'm looking for an oscilloscope that will not only allow me to do all of the typical, "lower-level" electronics work, but also more complex optics/photonics work with lasers in the future. In particular, some of the optics/photonics work will involve designing, building, and utilizing Q-switched Nd:YAG lasers and laser doppler vibrometers. The Q-switched Nd:YAG laser will operate with a pulse width of around 3ns and with an excitation wavelength of around 1550nm. I will likely also do some other optics/photonics work beyond this, such as with UV lasers such as nitrogen lasers at around 300nm and other frequency-tripled and quadrupled Nd:YAG work at around 200-400nm. Therefore, such an oscilloscope would need to be sophisticated enough to handle such a large breadth of work.The problem is that, since I've just started studying electronics and the associated physics, I don't have a good grasp of what oscilloscope I need for my work. I have seen someone recommend a Tektronix TDS 2024B 200 MHz for applications that closely resemble my work, but I'm unsure if this is suitable for me. Since oscilloscopes are so expensive, I'm looking for something that is as cost-effective as possible that will work well for my purposes. I have no problem problem buying second hand, as long as they're in good condition and will last over the long-term.Since, as I understand it, the people on this forum are so knowledgeable about oscilloscopes, I would really appreciate it if you could help me make this purchase. Thank you.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 09:14:55 am
content: What's the budget?

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 09:16:05 am
content: Quote from: Fungus on November 29, 2019, 09:14:55 amAs cost-effective as possible, but at this point I'm just trying to get an idea of price-ranges. I'm purchasing this out-of-pocket, so I want to get an idea of how much such an oscilloscope would cost.

author: BravoV
author_rank: Super Contributor
timestamp: November 29, 2019, 09:32:16 am
content: Quote from: 3rj4 on November 29, 2019, 09:16:05 amBy revealing the ball park number, knowledgeable people around here can be more accurate to suggest certain class/league of scope that suits your need.But by floating this number, expecting mobs will hammer this thread with useless craps starting from 20 bucks scope up to crazy expensive ones.0.5 cents worth of advice.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 09:34:06 am
content: Quote from: 3rj4 on November 29, 2019, 09:16:05 amIf you want to look at 3ns pulses then it won't be cheap. 200 MHz is nowhere near enough for that.

author: tautech
author_rank: Super Contributor
timestamp: November 29, 2019, 09:36:20 am
content: Quote from: 3rj4 on November 29, 2019, 09:07:31 amNope, for what a modern one can do they are cheap as chips.$500 US can get you something for life that has more features than was ever dreamed possible just 10 years ago.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 09:37:33 am
content: Quote from: Fungus on November 29, 2019, 09:34:06 amQuote from: BravoV on November 29, 2019, 09:32:16 amI'm aware that it will be expensive, but I'm hesitant to expose my total ignorance of this subject by throwing out a number. I'll put it this way: I'm expecting that a scope that satisfies my criteria above will cost as much as a brand new high-end personal computer. I hope that doesn't sound too ignorant.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 09:39:59 am
content: Quote from: tautech on November 29, 2019, 09:36:20 amWow, $500 US and works well for the purposes I explained in my post? That's a lot less than I thought (from what I've seen, I was thinking that it would surely cost over $1000 AUD) .

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 09:45:56 am
content: Quote from: 3rj4 on November 29, 2019, 09:39:59 amIt's true that $500 can get you something unthinkable 10 years ago but it won't be good enough for the things you mention.For a 3ns pulse you need a minimum of 1GHz, preferably 2Ghz if you want to see anything more than "there's a pulse there!".ie. You're going to be spending much more than $1000. At 2GHz just the probes will cost you more than $500.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 09:48:47 am
content: Quote from: Fungus on November 29, 2019, 09:45:56 amWould my previous estimation of a brand new high end personal computer be accurate? How much are we specifically talking about here?

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 09:53:11 am
content: Quote from: 3rj4 on November 29, 2019, 09:48:47 amWhat's "high end" to you?So far this thread is just "How long is a piece of string"?

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 09:53:59 am
content: Quote from: Fungus on November 29, 2019, 09:53:11 am$3000 AUD?

author: AndyC_772
author_rank: Super Contributor
timestamp: November 29, 2019, 09:54:16 am
content: You're doing the right thing by asking for advice here - but I'm afraid you won't like the answer.Optics is an area which can - and I stresscan- be extremely demanding in terms of scope performance. Think several GHz bandwidth, incredibly low jitter, active probes, and price tags well into five figures if you really want to monitor laser drive signals with the kind of precision that may be required.These are not instruments that you'll buy out of your own pocket, or on the advice of random strangers on the internet. You'll gain access to them as and when you have a specific need to make measurements that are well quantified in terms of bandwidth, precision and commercial benefit (ie. cost).When I was doing this kind of work, I had a 500 MHz Tek TDS754D, which was a fair compromise in terms of affordability vs ability to tell if a circuit was kind-of, sort-of, functioning OK. It could show that drive signals were being generated in the expected patterns, but couldn't tell anything about their true shape or timing on a sub-nanosecond scale.These days my usual bench scope is an Agilent MSO-X3104A (1 GHz). Like the Tek, it's more than fast enough for 95% of what I do, and nowhere near fast enough for the other 5%.

author: Someone
author_rank: Super Contributor
timestamp: November 29, 2019, 09:55:28 am
content: Quote from: 3rj4 on November 29, 2019, 09:07:31 amYou're taking lots about nm which have nothing to do with an oscilloscope, observing light requires special probes:https://www.tek.com/datasheet/dpo7oe-series-optical-probeshttps://www.keysight.com/en/pd-2746451-pn-N7004A/33-ghz-optical-to-electrical-converteror more general amplified detectors:https://www.thorlabs.com/navigation.cfm?guide_id=2171Quote from: 3rj4 on November 29, 2019, 09:37:33 amThe sensors/probes are likely to take that budget alone. A scope to observe a single pulse event, or a continuous repetition is entirely different, and what you wish to observe. Even a "cheap" equivalent time device has serious limitations:https://www.picotech.com/download/manuals/PicoScope9000QandA.pdfGenerally people wouldn't try and buy a scope that does everything imaginable, as its just too expensive.Quote from: 3rj4 on November 29, 2019, 09:48:47 amYou won't be able to make a reasoned choice in time for the "sales". Buying something without understanding what you need is just throwing money away, far better to spend some time to understand whats needed and then buy. The best advice is to borrow/loan/rent/trial some devices in your specific applications first before buying.

author: tv84
author_rank: Super Contributor
timestamp: November 29, 2019, 09:58:23 am
content: Quote from: 3rj4 on November 29, 2019, 09:48:47 amYou're going the wrong way! In a few pages, you'll find out that this is all about money so, before continuing, state your limits.

author: ebclr
author_rank: Super Contributor
timestamp: November 29, 2019, 10:12:53 am
content: Take a look on this scopehttp://www.saelig.com/product/mso5074.htmPrice is reasonable, quality is great, sampling is fast 8Gbs, firmware "so so"You don't get anything near on this price range, It a weel balance between price and performance for a professional middle advanced use, Us branding models with similar sample rate cost between 8 to 20 times moreAlso is hackable and easily goes to 480 Mhz max ( nominal 350 )It's a best bang for the buck on the pro area, following de famous DS1054 for entry-level scope, I have both and like

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 10:16:52 am
content: Quote from: Someone on November 29, 2019, 09:55:28 amInteresting, I didn't know oscilloscopes could be rented. Given the costs, that's probably the best way to go about this.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 10:26:34 am
content: Your answers have been highly informative and appreciated. I have some thinking to do. Thank you all for the help.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 10:39:40 am
content: Quote from: ebclr on November 29, 2019, 10:12:53 amI was also thinking of a hacked Rigol MSO5000. It has the sample rate and bandwidth to see if a 3ns pulse is happening even if it can't tell you much about it.Anything more than that is going to get crazy-expensive and could easily end up not being the right tool for the job (wrong probes or whatever).Better to gain some experience first with an all-round 'scope that can do the minimum and is great value for money.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 10:50:14 am
content: Quote from: Fungus on November 29, 2019, 10:39:40 amSo do you think that a hacked Rigol MSO5000 is the way to go initially? That way, I have something to use for my non-laser work, and it is also stillsomewhatinformative in experimenting with a 3ns laser (and potentially other lasers)?If so, would you recommend purchasing it fromhttp://www.saelig.com/product/mso5074.htm? Or can it be purchased within Australia? Is there anything else that I need to purchase along with this (probes, etc.)? And it is relatively simple to hack it myself by searching online and on this forum, correct?My apologies for the bombardment of questions.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 10:55:49 am
content: Quote from: 3rj4 on November 29, 2019, 10:50:14 amIt's what I'd do if I was spending my own money...Quote from: 3rj4 on November 29, 2019, 10:50:14 amI don't know where to buy them in Australia.Quote from: 3rj4 on November 29, 2019, 10:50:14 amNo.Quote from: 3rj4 on November 29, 2019, 10:50:14 amYes.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 11:04:13 am
content: Quote from: Fungus on November 29, 2019, 10:55:49 amLooks like I have my first oscilloscope. Thank you all for the help!

author: nctnico
author_rank: Super Contributor
timestamp: November 29, 2019, 11:08:22 am
content: For high speed there are several second hand options. The Agilent 54845A (1.5GHz) or a Lecroy Wavepro 7200A (2GHz) or 7300A (3GHz) are not extremely old. Both can be bought at the US $2k to US$3k mark and much less if it has some issues (there is lots of knowledge on this forum to fix both these scopes).For general purpose work you can look at the lower end scopes. Personally I'd stay away from recently introduced Rigol scopes; they take too long (years) to fix issues. You can take the chance ofcourse but be prepared to get stuck with issues and missing features that may be fixed after years (or never). If that doesn't affect your workflow then it is OK but for professional use I urge you to look beyond price and specs on paper. Chances are you might need to use a feature which should be there on paper but isn't really useful.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 11:45:18 am
content: Quote from: nctnico on November 29, 2019, 11:08:22 amThanks for the advice. I think I'm going to get the MSO-5074 as a first oscilloscope, and then potentially upgrade in the future if the need arises. A second-hand Agilent 54845A, as you said, seems to be relatively affordable, so that's something I'll keep my eye on in the future.

author: Shock
author_rank: Super Contributor
timestamp: November 29, 2019, 12:41:33 pm
content: Quote from: nctnico on November 29, 2019, 11:08:22 amI've never been that concerned with firmware especially if you go through a distributor, if a product has deal breaking bugs, back it goes and thanks for the free demo. Especially in Australia and the EU we have strong consumer laws to help. But the important thing is do as much research and test your gear as thoroughly and as quickly as you can, don't be an early adopter unless you are prepared to wait.No brand is immune from bugs but there are also ways you can escalate matters even in China. I'm in year five of a one year warranty for a particular (non EE) product I have here, and every time it fails we get to roll the dice all over again.

author: nctnico
author_rank: Super Contributor
timestamp: November 29, 2019, 01:00:06 pm
content: Quote from: Shock on November 29, 2019, 12:41:33 pmBut that depends entirely on the willingness of the distributor. A few years ago I lost about 2k euro on a non-working oscilloscope. The distributor was not willing to take it back at all. According to him I just had to wait until the firmware got fixed. The alternative was to take the distributor to court but that would likely cost more than 2k.The suggestion to test everyhting is a good one but not everyone has the knowledge to do that and time is also money. Testing an oscilloscope thourouhgly easely takes 2 or 3 days fulltime.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 01:31:02 pm
content: Quote from: nctnico on November 29, 2019, 01:00:06 pmQuote from: Shock on November 29, 2019, 12:41:33 pmYes, I'm not going to purchase it now as I'm busy with other work and don't yet have the electronics knowledge to fully test such a device, but I at least now have the knowledge of which one to purchase when I do. The peace of mind was worth it.

author: tggzzz
author_rank: Super Contributor
timestamp: November 29, 2019, 01:43:52 pm
content: Quote from: 3rj4 on November 29, 2019, 09:07:31 amOK, but what do you need to see in that pulse? Possibilities include:amplituderisetimerepetition intervalgeneral shapetime of occurrance relative to something elsemV, V, MVsensor output characteristics (voltage/current, impedance, connector, ...The last is important since it will indicate how you need to connect the sensor to the scope.As a rule of thumb, unless you know otherwise, expect to pay the same for the probes as you do for the scope. Even at RS/Farnell, probe prices range from £5 to £5k, and they aren't the most expensive!

author: Shock
author_rank: Super Contributor
timestamp: November 29, 2019, 01:52:17 pm
content: Quote from: nctnico on November 29, 2019, 01:00:06 pmI'm not sure about the specifics of what happened to you and what the issue was, sorry to hear you couldn't resolve it. But if I found a problem here in a reasonable time frame and it was not resolved (again within a reasonable time frame) consumer law wins out, there also is no statute of limitations on manufacturing defects here either. One thing that also happens A LOT is distributors and manufacturers often will push back automatically as hard as they can until you start escalating (and I don't mean internet posts) by writing proper demands. Remember they have to pay lawyers as well, meanwhile you probably have free consumer protection agencies and advocates you can contact. Here it costs them money when you start laying complaints.You have to always be civil and consistent in your approach. When they start ignoring you or give no dates for resolution etc at a management level that is basically abandoning any form of warranty. I have purchased countless of pieces of gear in a business capacity and personal capacity and oscilloscopes are no different from anything else with a firmware bug. Never had a problem but had many conversations where I've been told to contact the manufacturer if I have issues. I just tell them actually no I'll bring it back and you will remedy it or refund me or we can play credit card reversal lotto and see if my bank likes me or you better.I've been on the flip side of this as well but never left a customer hanging. It pays not to deal with nickel and dime distributors or small stores that don't have a communication path to the manufacturer for this exact reason. I once spent a nice afternoon with the state manager (insert brand here) test driving my new car and giving him feedback on the handling heh.

author: nctnico
author_rank: Super Contributor
timestamp: November 29, 2019, 02:12:30 pm
content: Well my purchase was a business one and the distributor turned out to be what we call 'a box shuffler' even though it was an official dealer. I had contact with the manufacturer as well but it turned out they where unable to do anything within a reasonable amount to time. Promises where repeatedly made and repeatedly broken.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 29, 2019, 02:44:42 pm
content: Quote from: tggzzz on November 29, 2019, 01:43:52 pmAll of the above, since I’d be looking to eventually design and utilize my own (so I’d obviously want to verify that it functions as intended).

author: TurboTom
author_rank: Super Contributor
timestamp: November 29, 2019, 03:20:32 pm
content: Designing an optical probe to properly characterize your laser output pulse (3ns duration as you specified, probably requiring rise/fall time resolution of a few hundred picoseconds) is a task of its own. Then, you need to be able to verify that your design approach is sound. Here we are quickly at a frequency requirement of 5+ GHz for the scope, and this is where high end terrain starts, accompanied by corresponding price tags.I guess starting off with a 1k scope and then working your way along getting used to it and learning what you can and what you can't use it for is a quite reasonable idea. With a year's time of experience, you will know much better what you need, what you can design and construct yourself and what your next step could possibly be that wouldn't break the bank. Even if you should find that the 1k scope doesn't fit your requirements during this time, it shouldn't be difficult to sell it with only little financial loss -- and a decent amount of experience gained.

author: Shock
author_rank: Super Contributor
timestamp: November 29, 2019, 03:37:15 pm
content: There is also one guy that always says RTFM.In the case of test equipment where a lot of us have had to do comparisons, becoming intimate with your desired oscilloscopes specifications/performance and capabilities before purchasing it allows you to make comparisons, it's also invaluable if you are going to become a serious user. I can testify to this and I'm sure there are others out there, I tend to be a happy consumer because I understand how the device performs prior to buying it. So yes there is something to be gained from not rushing in.There is a common theme is if you don't know what it does or what you need it for, you don't need it yet.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 03:55:38 pm
content: Quote from: nctnico on November 29, 2019, 11:08:22 amThat happens onalloscilloscopes, not just Rigols. Ask people here Who've bought $12,000 oscilloscopes if they're perfect or not.

author: nctnico
author_rank: Super Contributor
timestamp: November 29, 2019, 04:10:14 pm
content: Quote from: Fungus on November 29, 2019, 03:55:38 pmWell on a 12k scope basic features like hi-res just work at time of introduction. Sure some obscure bugs may take longer to spot but there is a significant difference between the low end B brands and the A brands. For professional use it makes lots of sense to spend the extra cash. After all time is money.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 04:20:20 pm
content: Quote from: nctnico on November 29, 2019, 04:10:14 pmHaters gonna hate.How do you explain all the people who are managing to look at signals with Rigols?Do you have alternative 'scope for $1000 with 350MHz+ bandwidth, 8GHz sample rate, 400Mb memory, etc.?(and with that post this thread now devolves into the usual phlegm-fest that always happens when somebody asks for 'scope advice)

author: Shock
author_rank: Super Contributor
timestamp: November 29, 2019, 04:27:17 pm
content: Quote from: Fungus on November 29, 2019, 03:55:38 pmI mentioned to him already before take it easy. I'm not up to date with all models just the DS1054Z and then not really, but it's been all in all pretty reliable considering the market penetration. Too bad they will all fail next year.Siglent and their promotional division Taupaki Technologies Ltd. NZ has spent considerable effort raising their brand image and I recall there was a few negative flurries around firmware. They always used to give off that GW Instek trashy vibe to me. Be a different story if I had one personally then in true Eevblog fashion I could say it's the best thing ever.Not specific to anyone here but my favorite one is when I hear people say I'll never by another ..... , or expensive ..... again and it's actually one of the better brands. Welcome to consumerism land.

author: DIPLover
author_rank: Regular Contributor
timestamp: November 29, 2019, 04:37:14 pm
content: Guy talks about photonics,Tautech comes running to shill $500 siglents.Classic.

author: nctnico
author_rank: Super Contributor
timestamp: November 29, 2019, 04:45:48 pm
content: Quote from: Fungus on November 29, 2019, 04:20:20 pmIt is simple: they don't know what they are missing.

author: tggzzz
author_rank: Super Contributor
timestamp: November 29, 2019, 04:51:09 pm
content: Quote from: 3rj4 on November 29, 2019, 02:44:42 pmYou're going to need to make a stab at answering the questions, numerically where possible. Without that, any suggestions are of dubious relevance to you.Details matter, and none of us here knowyourrequirements.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 04:53:02 pm
content: Quote from: nctnico on November 29, 2019, 04:45:48 pmOK, that's the snipe out of the way.Now the question: Your recommendation for an alternate, sub-$1000 'scope that can see 3ns pulses was...?

author: Shock
author_rank: Super Contributor
timestamp: November 29, 2019, 05:45:30 pm
content: Quote from: DIPLover on November 29, 2019, 04:37:14 pmIf he backed Rigol as well he could have retired by now. But watching the inner turmoil of which brand to recommend play out live on the forum would have been heartbreaking.

author: nctnico
author_rank: Super Contributor
timestamp: November 29, 2019, 06:14:54 pm
content: Quote from: Fungus on November 29, 2019, 04:53:02 pmWell, I paid $400 (ex shipping) for a slightly defective Lecroy Wavepro 7200A a couple of weeks ago (which is now working fine again). There are tons of other options out there from Lecroy, Tektronix, HP/Agilent which can be had for good bargains. Buying used is by far the best option to get a good high frequency oscilloscope. 3ns roughly translates to a 167MHz fundamental frequency. The required bandwidth depends on the amount of detail that needs to be displayed but 500MHz is likely barely sufficient.

author: james_s
author_rank: Super Contributor
timestamp: November 29, 2019, 06:46:35 pm
content: Quote from: 3rj4 on November 29, 2019, 09:48:47 amI have a hard time getting excited about anything less than 500MHz. If you go the new route then prices start around $12k for the big names like Tektronix, Keysight or LeCroy. If you look at the newer Chinese brands there are options as low as around $4k. This is of course why I've always bought used, I have under $600 invested in my 1GHz TDS784C but it's a bit of a boatanchor and I had to do some repairs to get it fully working. I'm also a fan of the TDS3000 series which can all be upgraded to 500MHz, they have quite low memory depth by modern standards but otherwise they are nice to use. I am admittedly a Tek fan though.Then there are probes, the basic passive probes that come with most scopes are suitable for basic stuff but they start to fall short at higher frequencies or more specialized tasks. You can easily spend thousands of dollars on probes and active FET probes are both expensive and fragile. Used is of course an option with probes too but it can be a gamble.Personally my suggestion would be wait until you need a scope and then start shopping for instruments that meet your needs at that point which is probably a year or more down the road. The other option is forget about getting the scope that will serve you in every need for the rest of your life and something cheap like the popular Rigol or Siglent scopes that are only around $400. You can do quite a lot with one of these, it will get you familiar with the fundamentals of a DSO and you will learn about the limitations and have a better idea of what you really need later on. Even once you've moved on, having an inexpensive little scope as a backup or secondary can be handy.Don't overlook the used market, old instruments may look big and clunky but if you are willing to deal with a big heavy box you can get performance that would cost tens of thousands new for a few hundred bucks.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 06:48:40 pm
content: Quote from: nctnico on November 29, 2019, 06:14:54 pmWas that with probes?How much for shipping to Australia?How difficult was the repair, what equipment did you need?

author: AndyC_772
author_rank: Super Contributor
timestamp: November 29, 2019, 08:08:59 pm
content: Quote from: Fungus on November 29, 2019, 03:55:38 pmMSO-X3104A here, virtually identical to the current 'T' model which right now is £12,337 here in the UK at Farnell.I've yet to find a bug in it.

author: Fungus
author_rank: Super Contributor
timestamp: November 29, 2019, 08:24:56 pm
content: Quote from: AndyC_772 on November 29, 2019, 08:08:59 pmThat doesn't mean there aren't any bugs, just that you haven't seen them.The firmware release notes are available for all to see:https://www.keysight.com/upload/cmc_upload/All/Keysight_2000A_3000A_X_Series_Oscilloscope_Release_Notes_02_50.pdfEight years after launch and they're still fixing things...

author: 3rj4
author_rank: Regular Contributor
timestamp: November 30, 2019, 01:32:34 am
content: Quote from: tggzzz on November 29, 2019, 04:51:09 pmI'm still at the initial stages of understanding what I need for my project, but, based on what I know at the moment, this specific Q-switched Nd:YAG laser would operate at a fixed wavelength of ~1550nm excitation wavelength, have ~3 ns pulse width, 3mm beam diameter, 1-25 mJ/pulse, 15 Hz. I'm not sure about the details beyond this, so you'll just have to fill in the blanks with what sounds reasonable for a project like this. Sorry for the vagueness.

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2019, 01:39:05 am
content: I'd focus on getting the requirements right before buying anything. You should have theorised the outcome from the experiment(s) you want to do and from that you should be able to set a clear set of requirements for the test equipment. Your setup smells like it is going to happen at a research facility; I suspect they have equipment over there as well or at least people who can give you a list with specs to look for. OTOH these person(s) may not be very aware of what is available in the market nowadays.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 30, 2019, 01:57:26 am
content: Quote from: nctnico on November 30, 2019, 01:39:05 amYes, I'm not going to buy anything until I have a solid understanding of what I need to measure. But, thanks to all of you, I now have a decent idea of what's available and for how much. The work that I've been describing here will not be part of my academic work, and will instead be my personal (non-academic) work, so I won't be able to utilize any university resources.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 30, 2019, 02:10:02 am
content: After comparing the Rigol MSO5074 to other scopes, it does seem that, after hacking, it isverygood value for the price. For more powerful scopes, it seems that the most cost-effective option would be to buy a second-hand scope, as some of you have suggested. And since this will be my first scope, I think getting a new MSO5074 is a wiser choice, since I can be more certain that it's functioning correctly, rather than buying something second-hand that I do not yet have the knowledge to fully vet.

author: BravoV
author_rank: Super Contributor
timestamp: November 30, 2019, 02:28:05 am
content: Quote from: 3rj4 on November 30, 2019, 02:10:02 amWhen buying an used scope, you have to rely on luck too, as you can't be sure as by the 2nd times you powered it on, its dead and can't be repaired (even you're capable of doing it) cause the unobtaininium chip inside is roasted, and this is not rare cases.A new scope that is covered by warranty is much more safer bet vs an used scope that can be dead "at any time", think about it if this worth.Also suggestions for buying used scope, mostly come from people that already have "another" working scope at their bench, and for pro. mostly thier existing scopes are still covered by warranty. Otherwise, its a suicide relying your bread & butter things purely on luck.Remember, assuming you're capable of fixing a broken scope, at most cases, you will need another working scope to help in fixing the broken one.

author: EE-digger
author_rank: Frequent Contributor
timestamp: November 30, 2019, 02:33:36 am
content: You're going to want a faster scope for 3ns or will not be seeing an accurate amplitude. I will not post a link but I have an 54846A on ebay at the moment. This model is 2.25GHz, not deep memory but for this type of application, fast pulses, repetitive, the memory is fine.On the probe side, you can do it on the cheap with a small active area InGaAs detector for the near IR wavelengths and a small area silicon for the shorter wavelengths. For a 3mm beam, a small area detector can simply be placed in the beam, perhaps at 8 degree angle or more to avoid back reflections if your laser has sensitivities to that.These PIN photodiodes can interface either to a simple 50 ohm load and zero bias voltage, or feed into a wide bandwidth transimpedance amplifier when you need more gain. If you are looking at collimated beams, you'll also need some attenuation but that can be handled by cheap or expensive methods.An older, fast scope will help you see your lasers for under $3k (scope only) and you can get a feel for what that bandwidth brings to the table.While a Rigol or other modern scope has a lot more goodies, the older scopes have everything you need and plenty of functions. The model I mentioned, for instance, has a floppy drive but was able to support USB flash sticks.I would go for bandwidth and avoid disappointment in not seeing your true signals. I've done a lot of fiber optic work at 1310, 1550nm and shorter wavelengths for fiber testing. The work went down to 5ns pulse widths in the 100mW range. All were fiber coupled which made life easier with detector mounts that had various standard fiber connectors.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 30, 2019, 03:46:57 am
content: Just found this:https://www.ebay.com.au/itm/HP-Agilent-54845A-4-Channel-1-5-GHz-8-GSa-s-Infiniium-Oscilloscope-0445/254433035190?hash=item3b3d6403b6:g:DYoAAOSwzCZd22-W#rpdCntIdI wonder if I could get it for $2500 or even $3000? It wouldn’t cost much more than the MSO5074, but it would be far more powerful and, as far as I can tell, probably powerful enough for my photonics work (and everything else I’d want to do)?The only problem is that I don’t yet have the expertise to make sure that it’s totally functioning correctly, so I worry that I’ll buy it and there’ll be something wrong with it. I’m not sure how quickly it’s possible for someone to learn all of this and to fully test the device (with the help of this forum, perhaps)?What do you all think?

author: james_s
author_rank: Super Contributor
timestamp: November 30, 2019, 04:26:06 am
content: Quote from: 3rj4 on November 30, 2019, 01:57:26 amYou're not allowed to use any university equipment in your own personal projects? That seems strange, I mean I can understand not being able to consume university supplies, but I'd have thought it wouldn't be too hard to find someone to loan you the use of a scope. I wouldn't be the least bit surprised if there's an old 1GHz+ boatanchor collecting dust in a closet somewhere at most technical universities.

author: james_s
author_rank: Super Contributor
timestamp: November 30, 2019, 04:35:00 am
content: Quote from: BravoV on November 30, 2019, 02:28:05 amIt's true that there is always a risk when buying used as-is gear, however I can say that I have come out ahead an overwhelming majority of the time and when you can buy 10 used scopes for the price of one comparable new one and have money left over that makes a pretty strong case for buying used. If it fails and you can't fix it, buy another one and sell the broken one on ebay, often times a broken scope will fetch half or more as much as one that works.The only time I would argue for buying new is when you have more money than time, or are working on something where the potential profit is more than enough to justify the cost of expensive equipment. I come from a world of spending my own pocket money on tools though so spending the equivalent of a new car is out of the question. That said, I don't buy new cars either, even if I didn't think they were crap I'd be happier to let someone else take the depreciation hit and break it in for me.

author: 0culus
author_rank: Super Contributor
timestamp: November 30, 2019, 04:37:58 am
content: Quote from: 3rj4 on November 29, 2019, 09:48:47 amThink more along the lines of a high end workstation than a PC. The Keysight MSO-X we have in the lab at work is 6 GHz and loaded with options. It cost $30 kilobucks to purchase new. To say nothing of active probes, which will easily run a few thousand apiece at a minimum.

author: 3rj4
author_rank: Regular Contributor
timestamp: November 30, 2019, 04:46:02 am
content: Quote from: james_s on November 30, 2019, 04:26:06 amThe problem is that, if you use university resources for a project that you eventually commercialize, then they technically have a legal claim to the project. This is something that I want to avoid.

author: james_s
author_rank: Super Contributor
timestamp: November 30, 2019, 04:55:29 am
content: Well that's annoying, I think if they're going to lay claim to anything you come up with, they ought to be paying you to be there instead of the other way around. Oh well, not much you can do about that I suppose.

author: Plasmateur
author_rank: Regular Contributor
timestamp: November 30, 2019, 06:51:51 am
content: Quote from: 3rj4 on November 30, 2019, 02:10:02 amI don't believe that scope has 50Ohm terminations, which is something you'll have to think about.Also the bandwidth only goes up to 350 MHz, so higher frequencies will be attenuated.There's no AUX trigger either, so you'll only get 4GHz bandwidth max if you would need to trigger one of the other channels for a time of flight application, or you can think of a fancy way around it.No 10MHz clock.Not sure what the bit depth is either, so if you have some small waveform buried in a large signal, that may be an issue for you as well.

author: tggzzz
author_rank: Super Contributor
timestamp: November 30, 2019, 08:38:48 am
content: Quote from: 3rj4 on November 30, 2019, 01:32:34 amThe type of laser, wavelength, beam diameter, energy/pulse are all irrelevant to the signal that will reach the scope. All the scope "knows about" is voltage and time.Getting the signal from the source to the scope requires understanding of the sensor's output characteristics and transmission lines or scope probes.You need to be able to specify the sensor's output before you can expect recommendations that are relevant to you.BTW, no, we don't have to fill in any blanks: you do.

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2019, 09:38:04 am
content: Quote from: BravoV on November 30, 2019, 02:28:05 amIf you need an oscilloscope to make money then you need to have two. Warranty is nice to get things fixed for 'free' but you'll still be without tools if you have only one oscilloscope and it is out for repair. Yes, I need an oscilloscope to make money and I make sure to always have a backup oscilloscope.

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2019, 09:45:15 am
content: Quote from: 3rj4 on November 30, 2019, 03:46:57 amYou can run the self calibration procedure on these scopes which is basically is a full self test for the acquisition system. If you need precission timing then it is a good tool.Shameless plug: I have a refurbished Agilent-54845A (which started life as a 54835A) for sale as well:https://www.eevblog.com/forum/buysellwanted/fs-agilent-54845a-4ch-1ghz-4gss-2ch-1-5ghz-scope-8gss/msg2755900/#msg2755900

author: Fungus
author_rank: Super Contributor
timestamp: November 30, 2019, 10:14:46 am
content: Quote from: BravoV on November 30, 2019, 02:28:05 amYep. Beware of tales on forums, gamblers only tell you about their wins not their losses.They also leave out details like "shipping costs" and whether or not it "came with probes" (probes can easily double or triple the price if you don't have any)In short: Buying second hand is a game for people who already have too many oscilloscopes/probes lying around the place.(and buying brandnewGHz+ oscilloscopes is a game for people who know for sure they're going to make money with them...)

author: Fungus
author_rank: Super Contributor
timestamp: November 30, 2019, 10:24:18 am
content: Quote from: 3rj4 on November 30, 2019, 03:46:57 amI'd still go for the Rigol as a base 'scope then look out for something second hand with high bandwidth. That way the high bandwidth 'scope can be very basic and you can maybe get away with only one probe.

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2019, 10:43:59 am
content: Quote from: Fungus on November 30, 2019, 10:14:46 amShipping costs depend highly on the shipper and location. And I still don't get people's obsession with probes. Do you really think a seller would put his/her best probes together with a scope they sell? I have news for you: they won't! All the probes I ever got together with a scope went straight into the bin. Nowadays I tell sellers to keep their old probes. Probes are consumables; they are prone to wear and therefore can develop all kinds of (intermittant) problems. Do you want to rely on that?Besides that if you are measuring high frequency / precission timing you make a direct connection to an oscilloscope. You are not going to hold a probe to a point in a circuit. IOW: for many high frequency measurements you won't be using probes at all.

author: Fungus
author_rank: Super Contributor
timestamp: November 30, 2019, 11:32:51 am
content: Quote from: nctnico on November 30, 2019, 10:43:59 amBut shipping boat anchors around between countries is never cheap.Quote from: nctnico on November 30, 2019, 10:43:59 amSimple: They're expensive, Oscilloscopes need them, people who are just entering the market don't have them.Your suggestion for a "sub $1000" oscilloscope really wasn't sub $1000, was it?

author: Fungus
author_rank: Super Contributor
timestamp: November 30, 2019, 12:16:15 pm
content: Quote from: Plasmateur on November 30, 2019, 06:51:51 amIt doesn't haveinternal50 Ohm termination but you can use a T piece and terminator, the difference will be tiny.You can't haveeverythingfor $1000, but the raw sample rates, etc. will go a long way..

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2019, 12:50:58 pm
content: Quote from: Fungus on November 30, 2019, 11:32:51 amThat depends. World wide shipping costs for the 54835A I have for sale is around 110 euro including tracking and insurance. I don't call that expensive.QuoteI'll make it more clear: you don't need probes. That is a misconception. There is a good reason why scopes are fitted with standard BNC connectors. And even if you need probes there are many ways to get into the GHz region without spending a whole lot of money. For example: I sell 1.4GHz differential probes for 125 euro (ex VAT ex shipping).

author: 3rj4
author_rank: Regular Contributor
timestamp: November 30, 2019, 01:11:22 pm
content: Quote from: Fungus on November 30, 2019, 10:24:18 amIf I can manage to get it for around $2500, I'm really tempted to just go for it. $1000 extra for something that is probably powerful enough to do everything I want seems like a very good deal. And there's no telling when the next time a scope like this will be available for this cheap in Australia.Is it realistic for me to use this forum to make sure that it's working properly, despite having never used an oscilloscope before?

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2019, 01:23:13 pm
content: Quote from: 3rj4 on November 30, 2019, 01:11:22 pmI'd ask the seller to run the self-calibration / self-test and send you the pictures of the result. To me it looks like the one from the seller is that latest version (VIN #33) that HP/Agilent made. It also has USB ports which is a plus. You might be able to get it for a reasonable amount of money. The seller has zero feedback as a seller which may put some people off (I think he/she copied the T&C from the listing of an equipment seller). Just don't start bidding early; wait until the last 30 seconds or less to put a bid in. This has two advantages: others won't be able to bid you up and you won't be tempted to put a higher bid in after being bid-up

author: 3rj4
author_rank: Regular Contributor
timestamp: November 30, 2019, 02:00:16 pm
content: Quote from: nctnico on November 30, 2019, 01:23:13 pmGood idea. I will do this and post the results here.Quote from: nctnico on November 30, 2019, 01:23:13 pmYes, I was planning on doing this.Thanks for the advice.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 30, 2019, 02:36:37 pm
content: Quote from: nctnico on November 29, 2019, 11:08:22 amrecently a member grabbed a 5GHz DDA5005 for just $900, no HDD... but i trust he can recover it. there were 2X $1.5K 6GHz SDA6000 now gone lucky guys who got them. i've spent i think around $1K on used probes alone (3 to 4 sets, bodies, heads and tips) there are 2 probe heads 5-6GHz are coming with excess tips all @ $600, and another $200 deskew fixture that i think i dont really crave for. but when you see others in the same range sell for many thousand(s) $, its like coming across a ton of gold that sell for like 10th or 100th of the market price, thats potentially can be reselled at the same or higher price. this is intoxicating beyond TEA that i ever experienced, i have 2 pcs of this WM/WP GHz range 20GSps DSO weigh 40 pound each in my possesion, i had another one that sold out a year ago, so i've touched (purchased) 3 enterprise grade stuffs, i feel like a large corporation, can you tell what kind of sickness is this?now you know... be carefull. ....ps: i thought the OP is firmed with a MSO-5074 scope on the first page but i see this thread keep going, so i'm just dropping my bomb herean owner of DS1054Z, LeCroy is just nice addition to fill the high end gap, fwiw..

author: BravoV
author_rank: Super Contributor
timestamp: November 30, 2019, 04:28:03 pm
content: Quote from: nctnico on November 30, 2019, 09:38:04 amPractically you are suggesting the OP, who doesn't know electronic at all, and probably doesn't have a clue how to use a scope in the 1st place, to buy a relatively expensive used scope as his 1st one ?

author: BravoV
author_rank: Super Contributor
timestamp: November 30, 2019, 04:32:41 pm
content: Quote from: Fungus on November 30, 2019, 10:24:18 am+1 , just use the "cheap" Rigol as a sacrificial scope for learning, as the OP just starting in electronic and doesn't have the full grasp on how to use a scope properly, let alone optimally.

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2019, 04:52:22 pm
content: Quote from: BravoV on November 30, 2019, 04:28:03 pmFrom the information provided it seems he needs one which has a bandwidth of at least 500MHz (and given the field he is interested in probably more) so there isn't much use to recommend a cheap one which isn't up to the task.And I'm sure a low end cheap scope isn't good for a beginner anyway due to the rough edges. Last week I had the non-pleasure of using a cheap Voltcraft DSO (probably an Owon or Hantek rebadge) and the thing just stops triggering every now and then. That just sucks if an oscilloscope is new to you because it seems the signal gets lost. This can cause a beginner to chase a non-existing problem in a circuit.

author: james_s
author_rank: Super Contributor
timestamp: November 30, 2019, 06:05:42 pm
content: Quote from: Fungus on November 30, 2019, 10:14:46 amI'm happy to tell of my losses, it does happen occasionally, that's why it's called a gamble. Still in the end when you add up the wins and the losses I have come out far, far ahead vs buying new. As in probably an order of magnitude or more in dollars spent.

author: TurboTom
author_rank: Super Contributor
timestamp: November 30, 2019, 07:16:17 pm
content: Quote from: 3rj4 on November 29, 2019, 09:07:31 amThis may sound somewhat precocious but the way this thread has developed, I just have to say that: Student pilots don't learn to fly on a jet fighter aircraft but usually on a single engine propeller plane or a glider.High speed oscilloscopes usually have quite delicate inputs that you can ruin by a simple mistake in your probing technique. If you haven't got any experience with scopes, a more simple and inexpensive one is the way to go. The mentioned MSO5074 or even a DS1054Z (or equivalent Siglent, GwInstek,... unit) will pretty much cover all your requirements of your first quoted sentence. And all this without much risk of ruining anything since these units only provide high-impedance inputs. Once you are familiar with this and got yourself accomodated in the "Art of Electronics" (btw that's a title of a book very recommended to get a copy of...), you should already know what you need to cover the requirements mentioned in your second sentence. I'ld just recommend to learn to walk before trying to run.That's not meant to discourage you but rather to keep your spendings reasonable and to avoid frustration.Cheers,Thomas

author: tautech
author_rank: Super Contributor
timestamp: November 30, 2019, 07:32:53 pm
content: Quote from: BravoV on November 30, 2019, 04:28:03 pmYep, that concerns me too.Nico OTOH has vast electronic and scope experience so for him to buy a used midrange scope is much less of a gamble while the OP apparently has very limited experience and also asks if the forum can guide him while learning how to use a scope.For starters the OP needs something easy to get screenshots from to then come here so we can hold his hand while he learns even the basics.Many of us have been using scopes for decades and most of us started with something cheap and often unreliable that we had to learn to fix and it soon became apparent that we needed a second scope too !In the bigger picture this becomes a significant investment in time learning how to fix our tools and having the tools to even do so ! It eats away at the time we have to even pursue our projects and can become a significant distraction from the tasks we have at hand.This is the road many of us here have traveled and many still do as we have gained the hard earned knowledge how to fix our gear should it need it.In hindsight many would agree to make an initial investment in one of the many compact DSO's the market offers today for the convenience of portability, capability, screenshots etc and use as a daily driver while we gain experience so the selection of a more capable and specialist scope can be wisely made somewhere down the track.Sitting where I am and with some knowledge gained from this discussion a midrange entry level DSO would seem the best solution for the OP as a stopgap until an instrument best fitting his requirements is needed.There are many new DSO's to $1k that could fit well as a good learning tool and ongoing investment on the bench.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 30, 2019, 08:29:30 pm
content: Quote from: BravoV on November 30, 2019, 04:28:03 pmthis line below will usually confuses many, including me, thats why i didnt jump in right away to answer, until someone else did suggest something of my fav...Quote from: 3rj4 on November 29, 2019, 09:07:31 amps: to OP, there is a member here selling his Agilent 500MHzhttps://www.eevblog.com/forum/buysellwanted/fs-(eu)-immaculate-agilent-msox3054a-full-opt-4500/if you dont like it here you may search equivalent in ebay or any other trusted site, but for the condition its 5 grand pounds and imho its still short at seeing your 3ns pulse at quite good delicacy... new @ 2K? forget it..

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2019, 08:35:07 pm
content: Quote from: tautech on November 30, 2019, 07:32:53 pmNow you make it sound like every expensive /higher end oscilloscope is difficult to operate. This just isn't true. For starters the older DSOs don't have decoding and complicated triggers. Because of that many older DSOs are actually easier to operate compared to a modern DSO. The HP/Agilent 54845A for example is pretty simplistic.There is ofcourse a risk in buying used equipment so getting some form of warranty may be worth the extra money.

author: james_s
author_rank: Super Contributor
timestamp: November 30, 2019, 10:21:47 pm
content: It is a good point that it's just as easy (if not easier) to blow up a $20k scope as a $400 scope, it should go without saying that one should not be trying to measure anything that is potentially high voltage or non-isolated until they really know what they're doing. If the goal is to look at an optical pulse then this should not be an issue but non-diode based lasers tend to have electronics that are practically ideal for damaging test equipment.

author: Plasmateur
author_rank: Regular Contributor
timestamp: December 01, 2019, 12:37:20 am
content: Quote from: BravoV on November 30, 2019, 04:32:41 pmBased on OP's knowledge of scopes, this really is the best answer.

author: Fungus
author_rank: Super Contributor
timestamp: December 01, 2019, 07:49:01 am
content: Quote from: TurboTom on November 30, 2019, 07:16:17 pmI'd say it was more like buying luxury used cars.Yes, there's a segment of the population who have the time, the tools, the workshop, etc., to go out and buy fancy used cars, run them for six months, sell on the ones they don't like, etc. They spend a lot of time scouring used car sites trying to find cars/parts at good prices, they get the occasional lemon but in return for those investments they get to drive nice cars (and go around telling others how little they paid for them).Is going out and buying a cheap/used luxury carwithout intending to become that sort of persona good idea? Not really. The probability that a car like that will be reliable for the next ten years and won't have any major problems is very low.So the question is: "Do you see yourself as an oscilloscope wheeler-dealer?"ntnico clearly is, and others are too. Itcanwork out if you're prepared to put the time/effort in but treat their advice accordingly.Quote from: james_s on November 30, 2019, 06:05:42 pmHow many oscilloscopes have you burned through, how many hours have you invested to get where you are today?Quote from: nctnico on November 29, 2019, 06:14:54 pmSame question as above.(and reading between the lines: You get through an oscilloscope every couple of weeks...)

author: nctnico
author_rank: Super Contributor
timestamp: December 01, 2019, 10:22:41 am
content: I don't go through an oscilloscope every few weeks. Usually an oscilloscope stays with me for a couple of years. And I had no real intention of buying the Lecroy 7200A but made a low ball offer (on Ebay) anyway. Much to my surprise the seller's counter offer was just too good to pass. Still that adds up to owning 4 oscilloscopes so at least one has to go.

author: Fungus
author_rank: Super Contributor
timestamp: December 01, 2019, 12:28:57 pm
content: Quote from: nctnico on December 01, 2019, 10:22:41 amShip it to Australia...

author: BillB
author_rank: Unknown
timestamp: December 01, 2019, 01:25:32 pm
content: Quote from: Fungus on December 01, 2019, 07:49:01 amBoth are apt analogies. My first thought was that of motorcycles. As an enthusiast myself, I spend a lot of time on forums trying to talk beginners out of buying a 1000cc superbike as their first. Obviously the consequences of a bad decision are quite a bit more severe than overbuying a piece of test gear, but the thought process is the same.Best case, one buys the bike rides it once then becomes deathly afraid and leaves it parked in the garage; its capabilities go unused. Worst case, well... the bike is totaled and worse.Sure, there is that veryrareindividual who can master such capabilities their first few times riding.The sagest advice in that scenario is start small, buy something to learn on, then sell it and move up. The market for entry-level, used bikes is hot and you'll usually make most of your money back when it's time to upgrade.The OP here is clearly shopping for a superbike.

author: tggzzz
author_rank: Super Contributor
timestamp: December 01, 2019, 01:49:24 pm
content: Quote from: BillB on December 01, 2019, 01:25:32 pmThe same is true for gliders. Orange flags are raised if the new-ish pilot has been successful in their high-flying (ho ho) career, and doesn't have the wit/humilty to realise that competence in one area means nothing about competence in another area.None of which appears to be relevant to the OP.QuoteI'd add that it is best to start on somethingsimple, without too many options - especially if the options are buried in a menu system. That's the opposite of a superbike, of course.My major concern is that the OP only comprehends some optical characteristics, and comprehends neither the corresponding electronic characteristics ,nor what measurements they need to make. Without the latter they cannot describe the required precision, which means any suggestions we make may well be inappropriate.

author: nctnico
author_rank: Super Contributor
timestamp: December 01, 2019, 03:40:13 pm
content: Quote from: BillB on December 01, 2019, 01:25:32 pmNo it isn't. Buying a car or motorcycle you can't control is dangerous. Buying test equipment which may seem overkill at first sight is not. At most it costs more money but even that is debatable when looking long term. A good tool is only a waste of money if you never ever use it. Otherwise it will likely enable you to do & learn new things and thus get ahead. Spending less only makes sense if you are not sure whether you want to persue a long term (hobby) career in a certain direction. Otherwise good tools will just add more pleasure to working on a project. It goes without saying that there will always be a limit to the budget as well.

author: Fungus
author_rank: Super Contributor
timestamp: December 01, 2019, 03:43:31 pm
content: Quote from: nctnico on November 30, 2019, 12:50:58 pmA misconception shared by most oscilloscope users?

author: nctnico
author_rank: Super Contributor
timestamp: December 01, 2019, 03:49:19 pm
content: Quote from: Fungus on December 01, 2019, 03:43:31 pmIt should be. In the end a probe is just a crutch to get a signal into an oscilloscope. For <100MHz probes work reasonably well and can be bought for a dime a dozen. Things change when the frequencies get higher or when dealing with low level signals. If I need to measure low level or high frequency signals I preferably use a direct connection. Also probes suck for longer term measurements. I have several open-ended coax to SMA cables which I can solder into a circuit.

author: BillB
author_rank: Unknown
timestamp: December 01, 2019, 04:27:53 pm
content: Quote from: nctnico on December 01, 2019, 03:40:13 pmOf course. I believe I mentioned that the consequences are more dire.Quote from: nctnico on December 01, 2019, 03:40:13 pmThis belies the stratification that exists in man's every endeavor of product manufacture. What is subjectively described asgood toolsis probably more accuratelygood-enoughtools. Pick any item on your workbench, in your toolbox or home - someone, somewhere is going to describe its low-quality shortcomings.One might argue that the oscilloscope is the most important piece of gear on the workbench and thus should be afforded a bigger budget. Perhaps, but one can't really say that about every item on the bench, right? There is a "starter" category in every product line imaginable and people judiciously purchase into and sell out from it all the time.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 01, 2019, 06:07:27 pm
content: Quote from: nctnico on December 01, 2019, 03:49:19 pmare you saying, manufacturers like lecroy or keysight are wrong when building their Kohm $K input impedance active GHz probe? there are more circumtances when we need to tap the already (built-in) terminated circuits with minimal loading. of course if you know the way around, you can get by just by using coax cable with some divider or splitter soldered on smd pads that supposed to be put a smd 50ohm terminator on it. but you yourself built your own active probe, how useless and misconception it is?ps: to OP, if he's not aware that those ghz dso input are 50 ohm and 5V max, he should look into this and decides if this will be suitable for his general purpose need or what. sometime even imagination can deceive, its interesting to hear some field like physics resonance or what, its like "i want to do this this is interesting!" but when we actually do the work and aware the difficulties involved, and other more expesive rigs needed, we may lose interest and DSO go unused (reselled).

author: james_s
author_rank: Super Contributor
timestamp: December 01, 2019, 06:08:47 pm
content: Quote from: Fungus on December 01, 2019, 07:49:01 am20 years ago I spent a few hours on a Tek 465B, it was an ebay gamble and ended up needing a new CRT, got one from Sphere though and used that instrument for ~17 years as my only scope.Then I spent about 5 hours fixing the TDS784C that has been my main scope ever since. That worked out well so I ended up buying about 5 different TDS300 and TDS400 scopes for lowball offers to play with. The TDS400 scopes didn't go so well, both have bad power supplies, I spent quite a few hours messing with them and set those aside for now, I will get back and finish those eventually. The TDS300 scopes worked better, one was an easy power supply fix and worked fine, the others just needed cleaning, sold one to a friend who didn't have any DSO. Then I took a step backward when I tried to back up the NVRAM and that somehow corrupted the calibration, I was able to calibrate the voltage part and got the scopes so they work well but complain that timing cal failed, I may still try to build something suitable to calibrate the timing or I may just unload those, I don't really need them, I only bought them for fun.Most recently I got a dead TDS3014 for free, that ended up taking about 2 hours to locate a bad oscillator which brought it back to life. Then to make it nice I replaced the display which had a delaminating rear polarizer and cleaned it up real nice and bought a new set of knobs for it. I bought a comm module which at $240 was more than I had invested in the whole rest of the instrument but that allowed me to upgrade it to a 500MHz TDS3054 so it was well worth it.Looking back over this I must have about $2,000 total invested in oscilloscopes over the past 20 years, and for that I have a 1GHz TDS784C and a 500MHz TDS3054 both fully loaded which are my daily driver scopes. I still have the 465B that I pull out mostly when I want XY mode. There are two TDS400 series and two TDS300 series in the closet that I could give up on and call failures if I wanted but like I said, they were bought in the first place to play with, not because I really needed them.So find me a brand new 1GHz 4 channel scope that I can buy for less than I've invested total in oscilloscopes in my entire life, even if I valued my time at something ridiculous like $300/hr. Good luck with that. $600+ 5 hours of my time, vs what, $15k? There's not even any comparison, it would be ludicrous for me to have taken any other route. Pay 25 times as much to get a warranty is a sensible? You've got to be joking.

author: james_s
author_rank: Super Contributor
timestamp: December 01, 2019, 06:17:53 pm
content: Oh and the used cars, that has worked out fantastically well for me too. 20 years ago I bought a Volvo 740 Turbo sedan for $500, the kid thought the engine was blown, it had a bit of water in the oil, it had 225k on the odometer, looked good though so I bought it assuming I'd have to swap the motor. I drove it for a bit and the oil cleared up so I proceeded to drive it daily for the next 17 years until a truck rear ended me and totaled it. I never did anything other than basic maintenance on it as needed. Oil changes, brakes, clutch, the most major work I ever did was pulling the cylinder head to repair some broken exhaust manifold studs and that was only a few months before it got wrecked. I've never been burned on a car, I've always bought used and I've owned only a handful of them. I don't buy with the intent to flip for a profit, I buy for the long haul and still have one I bought over 20 years ago. I've come out way, way, WAY ahead doing that. My cars have outlasted multiple cars they were replaced with by the previous owner.

author: Alfons
author_rank: Regular Contributor
timestamp: December 01, 2019, 07:36:59 pm
content: Ok, the thread drifts off a bit. But no matter. I too am one of those who look for used things, but that has less to do with not liking new things. It's just that there was a time when capable people developed great devices that are just too bad for the garbage. It has something to do with discovery, but also with respect for the performance of the engineers who have developed it. In addition to a Rigol DS1054Z are now a Tek744a and an Infiniium 54815 on my desk, both uphacked and both very fine devices, but I had to repair a little. It gives you a sense of what oscilloscopes should be like. Everything the two devices offer works as it should. Nothing superfluous, everything as it should. Ok, the little Rigol has less bandwidth and it's not a bad device, but it looks a bit miserable to the two, though packed with features. The problem is: once you have these devices in mind, you know what else is possible. And then it gets difficult and expensive. Maybe it's not so bad to stay with the Rigol and not get to know the other devices.

author: Plasmateur
author_rank: Regular Contributor
timestamp: December 01, 2019, 09:58:34 pm
content: Quote from: nctnico on December 01, 2019, 03:49:19 pmYou won't be able measure the floating potential of a low pressure plasma when terminated at 50 Ohms. At 1M Ohm the measurement will move closer to the floating potential. And if your Oscope has a 10M Ohm setting, it will likely be good enough. Most scopes don't have 10M Ohm internal terminations. And then if the plasma is time varying with high frequency components, an active probe will be needed. Probe tip to BNC/SMA adapters will be needed as well, otherwise the signal can be completely wrecked by noise.Then there is the issue of measuring current. Do you use two channels through a resistor, a current probe, or use some kind of inductive method and what kind of noise can that introduce into a signal?I take issue with how expensive probes are and want to say they aren't needed..... but then I would just be building my own probes, meaning for certain application they are absolutely needed.

author: nctnico
author_rank: Super Contributor
timestamp: December 01, 2019, 10:26:51 pm
content: Quote from: Mechatrommer on December 01, 2019, 06:07:27 pmThe probe I designed is a differential one. Unlike a regular probe this can measure a signal in respect to a non-ground reference or avoid ground noise. So far I have not used it myself (except for testing & validating the probe itself). I have not gotten to the projects I intended to use it on yet. One is checking the waveform across a low-side current sense resistor and the other is picking up a signal from a differential pair. In both cases my high-impedance differential amplifier box doesn't have enough bandwidth and high impedance isn't needed.Quote from: Plasmateur on December 01, 2019, 09:58:34 pmAt that point you are not speaking about a probe you can stick into a circuit but about a special pre-amplifier.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 02, 2019, 01:44:28 am
content: Quote from: nctnico on December 01, 2019, 10:26:51 pmregardless. you were saying, probe isnt needed which imho a misconception. there are diff active probes, there are simply active probes. diff probe can also be used as single ended measurement just as an acitve probe, and those have prices. that was the point of some members earlier. you can build 1/100x or 1/1000x high BW 50ohm probes using coax and some passive resistors, but that is just if you want to see some signals and cant afford active probes. btw, probes (active) discussion applies to both new or used dso, probes that usually comes with a new dso are useless for high BW. so you have to buy an active version anyway, and new will always need a fortune. here is a link from an old friend if you want to dodge a fortune...http://jahonen.kapsi.fi/Electronics/DIY%201k%20probe/

author: Plasmateur
author_rank: Regular Contributor
timestamp: December 02, 2019, 03:29:30 am
content: QuoteWhy is is considered a special pre-amplifier and not a 10M Ohm probe?Are you saying high impedance probes with a high frequency response aren't actually probes - but rather special pre-amplifiers?

author: nctnico
author_rank: Super Contributor
timestamp: December 02, 2019, 09:15:33 am
content: Quote from: Plasmateur on December 02, 2019, 03:29:30 amA probe is to poke around in a circuit. If you connect something directly then it is more like an amplifier. A direct connection is much easier to control (wiring, impedances) compared to a probe which uses an ad-hoc connection. A large portion of the price of a probe comes from needing to be small (hand held), relatively versatile, have low capacitances, etc.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 02, 2019, 10:56:21 am
content: What do you guys think? All good?

author: nctnico
author_rank: Super Contributor
timestamp: December 02, 2019, 11:21:39 am
content: Looks promising but the ultimate go /no-go is letting the self calibration run. There should also be an overview screen which says whether the trigger system and each channel has passed. The self calibration should be recent otherwise you will be looking at old data.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 02, 2019, 02:13:56 pm
content: Quote from: nctnico on December 02, 2019, 11:21:39 amWhat do you mean? Are you saying I should be requesting more pictures?

author: nctnico
author_rank: Super Contributor
timestamp: December 02, 2019, 05:03:28 pm
content: Quote from: 3rj4 on December 02, 2019, 02:13:56 pmYes. See this video for the screen.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 06:54:46 am
content: I won the HP/Agilent 54845A for 2225 AUD + 200 shipping! What do you guys think? Sounds like an amazing deal to me.

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 07:12:26 am
content: Quote from: 3rj4 on December 05, 2019, 06:54:46 amWith that price and capabilities, I guess its time to query for price quotation at local Keysight for calibration service maybe ?

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 07:14:48 am
content: Quote from: BravoV on December 05, 2019, 07:12:26 amHmm? What do you mean?

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 07:15:47 am
content: Quote from: 3rj4 on December 05, 2019, 07:14:48 amHow do you know that beast is still accurate ?Say you measure result at 10ns, actually is 15ns ?

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 07:16:28 am
content: Quote from: BravoV on December 05, 2019, 07:15:47 amCan I not test it myself?

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 07:17:54 am
content: Quote from: 3rj4 on December 05, 2019, 07:16:28 amNope, imagine you only have 1 DMM, and its bought "used" .. are you sure its still accurate ?

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 07:21:30 am
content: Quote from: BravoV on December 05, 2019, 07:17:54 amSo what do I need to do next?

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 07:25:13 am
content: Quote from: 3rj4 on December 05, 2019, 07:21:30 amSince this is a serious piece of test equipment, with "serious" price (at least to me), you want to make sure the money spent is worth right ?Since its "used", you just can NOT trust the seller claim that it is accurate or just because he/she said so, don't you ?So, in order to have "confidence" that it will measure "accurately", you need to send it to the manufacturer, in this case Keysight for calibration, meaning, to ensure its still up to it's specification, don't you want this ?

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 07:31:44 am
content: Quote from: BravoV on December 05, 2019, 07:25:13 amCould I not do this myself? For the record, I don't mind taking the time to (learn to) do it myself, rather than spending more money. I think that the knowledge gained would itself be very beneficial to my growth in EE. And it will help if I need to conduct repairs in the future. If I pay a professional calibration service to do it, then it costs me more money (remember, I am still a student), and I don't gain any of the knowledge that I otherwise would have.

author: maginnovision
author_rank: Super Contributor
timestamp: December 05, 2019, 07:34:43 am
content: It'll probably cost more to do it yourself and still not be done well as opposed to sending it off.

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 07:36:57 am
content: Quote from: 3rj4 on December 05, 2019, 07:31:44 amNope, as for calibration (means, to make sure it is still accurate) must and can only be done by the manufacturer. Unless you have the proper equipments fot that, which I think could be cost more than your scope.What happened if you measure 10mV amplitude, while actually its 12mV ? That already 20% miss, or say the pulse you measure is 10ns, while actually is 15ns, that is 50% inaccurate, you don't want this in your upcoming "serious" research right ?With the depth of your pocket there, it should be cheap.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 07:40:44 am
content: Quote from: BravoV on December 05, 2019, 07:36:57 amI see. How much does calibration cost? Must it be done by the manufacturer? I see numerous companies claiming in my area claiming to do "NATA accredited" calibration of oscilloscopes; could I not just use their services?Unfortunately, I do not have deep pockets; I am but a poor student. The reason I spent this money on the oscilloscope is because I am committed to pursuing various (commercial) projects that I have been working on for a while. This was an investment.

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 07:40:56 am
content: Fyi, since you're successfully "lured" by one of the poster here to buy an expensive "used" scope, hopefully the scope came with "proper" probe too.If not, suggesting you contact that particular poster, as he builds and sell his own made probe.

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 07:42:37 am
content: Quote from: 3rj4 on December 05, 2019, 07:40:44 amJust do a 'formal' query to Australia Keysight, if I were you, as this is the "best" to ensure your scope accuracy.Regarding other companies, I guess you should start to ask around too.

author: Fungus
author_rank: Super Contributor
timestamp: December 05, 2019, 07:48:16 am
content: Quote from: BravoV on December 05, 2019, 07:15:47 amIt seemsveryunlikely.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 07:49:24 am
content: Quote from: BravoV on December 05, 2019, 07:40:56 amWhat do you mean "lured" ...? This scope fits my requirements well, and costs almost the same amount as the MSO5074, which is much, much less powerful, and cannot accomplish many of things that I want a scope for.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 07:50:18 am
content: Quote from: Fungus on December 05, 2019, 07:48:16 amShould I be worried? Or is he just exaggerating?

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 07:51:20 am
content: Quote from: Fungus on December 05, 2019, 07:48:16 amYeah, still possible though, my point is, with this serious gear, one must have confidence in the 1st place right ? Especially its the only scope around.

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 07:52:51 am
content: Quote from: 3rj4 on December 05, 2019, 07:49:24 amJust forget I said that, just wishing you good luck with that.

author: Someone
author_rank: Super Contributor
timestamp: December 05, 2019, 08:06:40 am
content: Quote from: 3rj4 on December 05, 2019, 07:50:18 amThey are winding you up. Accuracy outside calibration from the manufacturer is as good as you need it to be, if you want to be sure any specific measurement is accurate you start by checking a known accurate source with the scope.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 08:10:31 am
content: Quote from: Someone on December 05, 2019, 08:06:40 amThanks. I was starting to get worried.

author: Fungus
author_rank: Super Contributor
timestamp: December 05, 2019, 08:25:51 am
content: Quote from: BravoV on December 05, 2019, 07:51:20 amI though the whole point of buying "serious gear" was that you always have that confidence?

author: BravoV
author_rank: Super Contributor
timestamp: December 05, 2019, 08:42:24 am
content: Quote from: Fungus on December 05, 2019, 08:25:51 amOnly new one and covered by warranty.

author: tggzzz
author_rank: Super Contributor
timestamp: December 05, 2019, 09:27:03 am
content: Quote from: 3rj4 on December 05, 2019, 08:10:31 amThe point at which you have to be worried depends on thepurposesfor which a measurement will be used -and we don't know that.To take a different example... If you have several voltmeters, they will always read slightly different values - so which is correct?Usually the absolute value is not very important; stability is more important. It is cheap and easy to get them to all read the same value: just have one stable voltage source, and twiddle each meter until they read the same.It becomes expensive and difficult when you want your meters to read the same value as everybody else's voltmeters. At that point you have to twiddle your meter to the same value as other people's meters - and that means the voltage source has to be an external common standard, which is expensive.

author: Shock
author_rank: Super Contributor
timestamp: December 05, 2019, 09:28:43 am
content: Let me explain it...Calibration is a check to see if the device is operating within it's defined parameters.When scopes are new they often have a manufacturers calibration and or a certificate (which may include a report or the results). They may also specify the frequency or time at which the calibration or certification expires and is no longer considered accurate or valid.After several calibrations are performed this builds up confidence that the equipment is operating normally (as you can see drift from the specifications over time). Some scopes have a self calibration, they may check themselves or even adjust themselves to remain as accurate as possible. This does not replace a full calibration check from a manufacturer or third party.If the equipment fails calibration, to restore it back within it's specified accuracy, it either needs adjusting to be within calibration or repairing. Otherwise it will be only as accurate as it's last check or possibly worse. Calibration equipment typically is collectively more expensive than the equipment being calibrated as it is also been checked periodically for calibration and has a higher accuracy and tighter specification.Traceability is another aspect of calibration/certification it and it's basically to ensure noone fudges the figures. The flow goes something like this. Standard ==> Transferred Standard ==> Calibration Device ==> Equipment being calibrated.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 09:53:20 am
content: Quote from: tggzzz on December 05, 2019, 09:27:03 amQuote from: Shock on December 05, 2019, 09:28:43 amInteresting. Thank you all for the information.This scope was last calibrated in2004:https://i.ebayimg.com/images/g/vxIAAOSwGzBd22-u/s-l1600.jpgSo I probably should go and get it calibrated.

author: Shock
author_rank: Super Contributor
timestamp: December 05, 2019, 10:15:01 am
content: Do you need secondhand equipment to come calibrated? Yes if you want to ensure it's accurate. No if it's still in calibration or was recently or you don't care. Ensuring it at least passes internal calibration and self tests is a good start though.If the seller is unscrupulous they may sell/ditch the equipment because it cannot be easily recalibrated. So there is some advantage in getting a calibration check done sooner than later. Obviously if you need a calibrated instrument, you need to factor calibration costs ahead of time.If you have access to similar or better calibrated equipment and you have or can make a suitable circuit to test, then you can make a comparative calibration check. This is generally the poor mans calibration route but at least gives you a rough idea.

author: Fungus
author_rank: Super Contributor
timestamp: December 05, 2019, 10:49:41 am
content: Oscilloscopes aren't multimeters. Oscilloscopes have self-calibration against built-in references.The chances of the internal references going out of spec is very veryverysmall and usually detected by the diagnostics.ie. These:Unless you see something obviously wrong when it arrives then I'd give it the benefit of the doubt.

author: tautech
author_rank: Super Contributor
timestamp: December 05, 2019, 11:04:48 am
content: Quote from: Fungus on December 05, 2019, 10:49:41 amWhen the OP has little idea of how to even operate a scope let alone an advanced one.His safest course of action is to have its performance verified as meeting datasheet spec.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 05, 2019, 11:22:28 am
content: Quote from: 3rj4 on December 05, 2019, 08:10:31 amtell you what. there is possibility when its arrived, its showing half the magnitude, or its PSU smoked, or its clock non locked, or its simply DOAyou ask people here, they will tell you the worst possible nightmare. if its me, i will just enjoy the purchase, if not, return it. or spend half the money i can afford, if its not expected, buy another one with more cautious. anyway, did you win the AUD3000+ DSO?https://www.ebay.com.au/itm/HP-Agilent-54845A-4-Channel-1-5-GHz-8-GSa-s-Infiniium-Oscilloscope-0445/254433035190?hash=item3b3d6403b6:g:DYoAAOSwzCZd22-W#rpdCntId

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 12:02:51 pm
content: Quote from: Mechatrommer on December 05, 2019, 11:22:28 amThat's the one, but it's only 2400 AUD (including shipping) - not 3000+ AUD.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 12:13:16 pm
content: Quote from: tautech on December 05, 2019, 11:04:48 amSince you seem to work in this space, and you're based in NZ, what is your estimation of how much this will cost me (I'm based in AUS)?

author: Fungus
author_rank: Super Contributor
timestamp: December 05, 2019, 12:23:02 pm
content: Quote from: 3rj4 on December 05, 2019, 12:13:16 pmIf you have to ask, you can't afford it.

author: BillB
author_rank: Unknown
timestamp: December 05, 2019, 12:34:19 pm
content: Congratulations on winning your auction for thatused superbikereally nice oscilloscope! Given that you have no specific job yet for which you'll need this scope, and you have some sensitivity to budget, why worry about calibration yet?As others have suggested, examine the scope for obvious problems, but otherwise if it passes self-tests and sensibly performs whatever measurements you can figure out at this point, just spend some time with it learning about oscilloscopes before you go sinking even more money into it.As you explore the scope and its capabilities, you can use this forum as a resource for troubleshooting if things don't behave like they should.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 12:36:43 pm
content: Quote from: Fungus on December 05, 2019, 12:23:02 pmI've seen catalogues price it at $180 USD? That's 10% of the cost of the scope itself.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 12:41:38 pm
content: Quote from: BillB on December 05, 2019, 12:34:19 pmSounds good. Gaining a deep understanding of how the scope works will surely have a lot of crossover with other aspects of electronics, so I think it will be a very productive endeavour!

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: December 05, 2019, 12:46:56 pm
content: Quote from: tautech on December 05, 2019, 11:04:48 amThese kind of threats pop up from time to time, with a lot of response all giving the "best advice". In the early days we had a name for that ..

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 05, 2019, 01:26:53 pm
content: Quote from: 3rj4 on December 05, 2019, 12:36:43 pmthat probably only for renting a space in their calibration lab, Keysight et al are known for their "fabulous" after sale service charge. you are talking 10% of "used" price. its new price is like 8K i guess, so expect something like AUD800. but thats just a wild guess. i recently bought an used spectrum analyzer, its calibration cost is 150% from what i paid for the unit. now that should start to worry you

author: tggzzz
author_rank: Super Contributor
timestamp: December 05, 2019, 02:06:20 pm
content: Quote from: 3rj4 on December 05, 2019, 12:36:43 pmYou need to understand the difference between "calibration" and "adjustment". Roughly speaking calibration means comparing to specification and noting where in/out of spec, whereas adjustment means twiddling it until it is in spec.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 05, 2019, 04:15:55 pm
content: Quote from: Mechatrommer on December 05, 2019, 01:26:53 pmQuote from: tggzzz on December 05, 2019, 02:06:20 pmThanks for the clarification. If it's really that expensive, then I'll just have to make do without it. Anyway, as the guys above said, as long as it passes the self-tests and has no obvious problems, I'm guessing it will be fine for my work.I'm curious to learn about how such a device is maintained to function well. These are expensive devices in the first place, so I'm guessing that you guys don't go around paying for calibration in addition to that, so what do you do to calibrate it when you notice that there's problem? Given the amount of time people put into personally repairing their expensive scopes, surely there's something you guys do for calibration too?I'm keen to start studying some oscilloscope-specific material (in addition to the other electronics material I'm studying), so if you guys have any textbook suggestions, I'd appreciate it. Something less technical to start off would probably be best, but then I'd like to jump into some technical material that will really give me a deep understanding of the device, so those recommendations are also appreciated.

author: tggzzz
author_rank: Super Contributor
timestamp: December 05, 2019, 04:30:35 pm
content: Quote from: 3rj4 on December 05, 2019, 04:15:55 pmFirst you decide what you need to achieve.Second you understand the consequences of different courses of action.Third you decide which course of action is appropriate.No, it isn't easy. Yes, it does take time and experience.

author: Shock
author_rank: Super Contributor
timestamp: December 05, 2019, 05:57:34 pm
content: After double checking all the self test pass yourself, and then perform functional tests you can do the self calibration. It will explain all this in the manual with the procedure to follow and what you need, if you get stuck I would start a new thread.As explained it's not a definitive calibration but it might be able to detect if any problems are found. You might also be able to look at logs and stats to determine the history of the oscilloscope. Just depends on the oscilloscope they vary model to model.Some people on the forum acquire calibration equipment so they can perform their own but it can get expensive especially the more advanced the oscilloscope is. If you have a service manual for your oscilloscope it may detail the calibration adjustment procedure. Sometimes the service manual/manual are one in the same, sometimes the manufacturer does not make the service manual public, sometimes it's just the schematic not released and often you can find it all on the web.Eevblog has a US calibration club, I'm not sure whats in the latest one or even if it's suitable for oscilloscopes. Besides that you aren't in the US, you're new and you need more experience. My advice is to completely absorb the manual and service manual and you will learn a lot. If you are unsure of terms look them up on the Keysights website and look for literature around the time the oscilloscope came out and about it's capabilities. If you know where every function is on the oscilloscope and can watch a video of someone using one and understand where that feature is on yours and your scopes limitations, that is half the battle. The rest is practical measurement techniques and interpreting what you are looking at.

author: tautech
author_rank: Super Contributor
timestamp: December 05, 2019, 07:51:14 pm
content: Quote from: JohnnyBerg on December 05, 2019, 12:46:56 pmErr, well the OP clearly stated he had zero scope experience and requires ns accuracy yet still spent $2k+ on a used scope. Could it have previously been abused or damaged from an instant of carelessness we may never know.Formal performance verification (advanced checks) by one of the many Cal labs will identify potential faults and then give the owner options to re-Cal (adjust) or have it repaired.Without a good understanding of the risks of buying something used and the potential costs for correction of a faulty instrument the poorly informed buyer can be setting themself up for unforeseen additional costs.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 05, 2019, 11:14:22 pm
content: as a beginner, we just measure whatever we want to measure. if there is signal, we are happy enough. forget about anything that cost us $$$ that we have less appreciation about. he will know when he needs a full scale calibration. by that time, he will and should be willing to find money for that. if not enough money, we will find workaround, improvise and use every bits of our imagination to deal with it. at least thats how myself is..

author: nctnico
author_rank: Super Contributor
timestamp: December 06, 2019, 01:17:36 am
content: Quote from: tautech on December 05, 2019, 07:51:14 pmThat is true up to the point where a piece of equipment can do a thourough self test. The Agilent 54835A / 54845A / 54846A can do such a self test. If it passes this self test then you know you have a working scope.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: December 06, 2019, 12:02:26 pm
content: I'm in the self-test and self-verify camp. If your scope passes the self tests and self calibration then try it on a known good signal e.g. a signal generator set to 100 kHz and 5V pk-pk. If what you see on the screen matches what you sent in then there's a very high chance that calibration is good. If you have customers who want to see your calibration certificates then send it in to the manufacturer.The last piece of gear I had calibrated was a Keysight 34461A $1,200 bench 6.5 digit multimeter, the cost was $125 plus shipping 1 way.I bought a board called the DMMcheck (seehttp://www.voltagestandard.comandwww.dmmcheckplus.com) which has calibrated DC and AC outputs plus four calibrated 0.1% resistors. You might consider one of those?

author: Fungus
author_rank: Super Contributor
timestamp: December 06, 2019, 12:24:38 pm
content: Quote from: Gandalf_Sr on December 06, 2019, 12:02:26 pmThat's for checking DMMs, not oscilloscopes. Oscilloscopes need a frequency check much more than they need a voltage check.Unless the scope has been zapped though, it's very unlikely to be wrong. Just use it for a while before deciding to spend money. Investigate only if some readings are obviously wrong.

author: SMdude
author_rank: Frequent Contributor
timestamp: December 06, 2019, 12:45:49 pm
content: Quote from: 3rj4 on November 30, 2019, 01:57:26 amNow you might not be able to use uni resources for your project, but I bet they have a good calibrated scope that you could compare yours to. At this point in time I would not get too excited about sending it off to have it calibrated.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 06, 2019, 03:55:56 pm
content: Quote from: SMdude on December 06, 2019, 12:45:49 pmAhh, that’s a good idea!

author: 3rj4
author_rank: Regular Contributor
timestamp: December 17, 2019, 02:49:13 pm
content: Ok, the scope arrived.It didn't come with any manuals, but I found this:https://www.manualslib.com/manual/642443/Agilent-Technologies-Xx3625.html?page=5#manual. Is this what I should be studying?

author: Shock
author_rank: Super Contributor
timestamp: December 17, 2019, 07:28:01 pm
content: All the docs are on Keysights website. I see user manual, quick start guide, service manual, programmer reference guide etc. Go to keysight.com click support and enter your model number.

author: 3rj4
author_rank: Regular Contributor
timestamp: December 17, 2019, 09:24:52 pm
content: Quote from: Shock on December 17, 2019, 07:28:01 pmAhh, I thought it required a login, but it only required a name and email. Thanks for that!

author: 3rj4
author_rank: Regular Contributor
timestamp: December 19, 2019, 07:04:50 am
content: What power supply do you guys suggest for my purposes?

author: tautech
author_rank: Super Contributor
timestamp: December 19, 2019, 08:09:01 am
content: Quote from: 3rj4 on December 19, 2019, 07:04:50 amWalwart......no but really you need to give requirements.Voltages and current specs and resolution required.Parallel and Series capabilities.# of channels.Sense requirements.Analog or digital display.Remote control capability.....LAN, GPIB etc

author: tggzzz
author_rank: Super Contributor
timestamp: December 19, 2019, 08:45:01 am
content: Quote from: 3rj4 on December 19, 2019, 07:04:50 amI suggest you define purposes/specs, search this forum, and start a new thread so that other people coming along later can benefit from the discussion.This forum isn't a transient place like Farcebook or some of the other electronic forums

author: 3rj4
author_rank: Regular Contributor
timestamp: December 19, 2019, 10:09:35 am
content: Quote from: tautech on December 19, 2019, 08:09:01 amQuote from: tggzzz on December 19, 2019, 08:45:01 amThanks for the advice. I was wondering if it would look bad if I kept making threads to ask questions about other equipment, but I guess I have my answer. I will make a new thread.

author: nctnico
author_rank: Super Contributor
timestamp: December 19, 2019, 10:49:11 am
content: No need to make a new thread. This thread is recent and lists most of the options for a PSU:https://www.eevblog.com/forum/testgear/spd3303x-e-vs-dp832/

author: tggzzz
author_rank: Super Contributor
timestamp: December 19, 2019, 11:51:21 am
content: Quote from: 3rj4 on December 19, 2019, 10:09:35 amUltimately it is a judgement call and a matter of taste.But it is always worth doing research, partly for the reasons outlined herehttps://entertaininghacks.wordpress.com/library-2/good-questions-pique-our-interest-and-dont-waste-our-time-2/Many of those points do not apply to you!

author: Shock
author_rank: Super Contributor
timestamp: December 19, 2019, 01:05:47 pm
content: Quote from: 3rj4 on December 19, 2019, 10:09:35 amA new thread for a new topic is polite forum etiquette.