Affordable and portable oscilloscope? - Page 1
Forum section: electronics / testgear

author: AznGothic
author_rank: Contributor
timestamp: March 14, 2014, 11:17:06 am
content: First I'd like to start off by apologizing to who ever is in the YouTube video's. I sent you a message on youtube and THEN noticed your "please don't send me messages asking for advice" bit. So per your advice/request, here I am on the forums. I hope someone can give me a rather simple/quick answer since I am on a 1 week deadline for this.From watching the youtube video's I know you really hate pocket/PC oscilloscopes. But I'm not doing anything real fancy. I'm not an electronic engineer or anything. However, I do need some advice.I run a car audio shop here in the USA. All I need to do is test a tone coming out of a radio or amplifier to see the sine wave as I turn up the gain on the radio or amplifier. This way I can tell when the signal starts to clip and I'll know what the maximum clean signal of the radio or amplifier is. I know good quality oscilloscopes are expensive and are out of my financial capability. Also in my opinion they are a bit over the top for my purpose. I would really love to buy a TPI 440 or something similar but even that is out of my financial capability. Now I did watch the video where you tested the Q-DSO and that thing was complete rubbish. That would be the very example of what I DON'T want. I've found a few PC based oscilloscopes (Hantek and SainSmart mainly) under $100 USD but I don't know anything about them or what I should be looking for in specs (not to mention manufacturer's usually lie on specs anyways.)Could someone recommend a cheap portable oscilloscope that would serve my purpose? I need to be able to see when a signal (mainly 40Hz or 80Hz but will also be testing upwards of 1KHz) is clipping. The amplifiers I need to use this on range from 200 Watts to 2,000 Watts. Most of the amplifiers will be around 800 Watts to 1,200 Watts. I don't mind if it is a handheld or a USB/PC type as I do have a laptop I can take out to the vehicles with me. All I care is that it works and shows me when the signal is clipping (and doesn't have a crap load of noise in it like that Q-DSO reviewed in the video.) Oh, and being under $100 USD would be awesome if possible.

author: Mark_O
author_rank: Frequent Contributor
timestamp: March 14, 2014, 01:49:09 pm
content: Quote from: AznGothic on March 14, 2014, 11:17:06 amA Hantek 6022BE would do what you need, as long as you have a laptop to plug it into. They run about 70 bucks on ebay. There'ssome enhanced softwarebeing developed here on the forum by RichardK.Also, if you enable the FFT display, you'll probably be able to see the spurious harmonics appearing from overdrive distortion, before you could detect visible deterioration of the waveshape.

author: AznGothic
author_rank: Contributor
timestamp: March 14, 2014, 08:37:23 pm
content: That would be one of the ones I was looking at. Is Hantek made by SainSmart? Because I found it on their website. Also I found this chart on one of the Amazon listings for a SainSmart DDS120.What is the Gain Range? I thought I knew what that meant (The 1600W amplifiers put out 40ACV at 1ohm so I would need an oscilloscope with the 5V/50V range?) but the Hantek spec just says 10mV - 5V, 9 steps....so now I'm thinking I -don't- know what the gain range means. And I have no clue what you mean by the FFT display lol. I'm an amateur/noob when it comes to oscilloscopes. I've always wanted to get one and learn to use it but have always been a bit intimidated by oscilloscopes (and their price tag). But I like to offer my customers the best service possible which means properly tuning their amps, not just doing it by ear. I know there are two things to look for while tuning. One would be the clipping at the peak of the wave and the other would be the distortion in the rise and fall of the wave. Is that what you mean by the spurious harmonics from overdrive?

author: kc9qvl
author_rank: Regular Contributor
timestamp: March 15, 2014, 12:43:32 am
content: Have you thought about a hand held scope. Like this onehttp://www.sainsmart.com/tools-equipments/oscilloscope-dso/owon-hds1021m-20-mhz-handheld-digital-storage-oscilloscope.htmlor the uni-t ut81bhttp://www.uni-trend.com/ut81b.html

author: AznGothic
author_rank: Contributor
timestamp: March 15, 2014, 02:26:00 am
content: Yes I have. As I said, I really wanted to get a TPI 440 since I have heard a lot of good about it for my line of work and a lot of people use it for this (especially since it has built in True RMS readings)http://www.tpieurope.com/440.html#&slider1=1But I can't afford that price tag. I really need it to be $100 or less (I can go a little bit above $100 if need be.)

author: VK5RC
author_rank: Unknown
timestamp: March 15, 2014, 02:48:30 am
content: If a sine wave is clipped in any way it produces frequencies at a multiple of the original frequency (harmonic distortion or THD if you add them all up), these really stand out on a spectrum analyser (which some scopes can do to a limited degree using the maths of FFT). You will see the distortion generally much earlier on the Spectrum Analyser (or scope in that mode) than you will on the plain scope.

author: AznGothic
author_rank: Contributor
timestamp: March 15, 2014, 04:21:38 am
content: Thank you for clarifying that VK5RC. So what it sounds like is if someone came to me wanting a system for an SQL competition I would definitely want a spectrum analyzer or a scope with FFT but at the moment I just need a standard scope.So what is the whole "gain range" thing about in the pic I added? Will the Hantek 6022BE work for a 1600W amplifier that is putting out 40V? Or should I go with the SainSmart that says 5V/50V/500V? Is SainSmart even any good?

author: pickle9000
author_rank: Super Contributor
timestamp: March 15, 2014, 04:40:08 am
content: A 10x probe will allow you to measure up to 50v, you could also buy an external attenuator or a 100x probe to allow you to measure greater voltages.The software that richardk (on this forum) is developing has FFT, you can find that thread here.https://www.eevblog.com/forum/testgear/hantek-6022be-20mhz-usb-dso/The thread is long but you may want to read it, it's interesting.

author: BravoV
author_rank: Super Contributor
timestamp: March 15, 2014, 04:50:17 am
content: Do these cheap hand held scopes have isolated input & "ground" between the two channels ?

author: EEVblog
author_rank: Unknown
timestamp: March 15, 2014, 07:24:23 am
content: Quote from: AznGothic on March 14, 2014, 11:17:06 amWhy would you even consider PC based scope when you want a portable scope?Just buy any hand held scope out there and it will do what you want, or one of the multimeter/scope combos.http://dx.com/p/ut81b-3-2-lcd-digital-multimeter-red-black-4-x-aa-113631?tc=AUD&gclid=CLKXr4ODlL0CFYHxpAodAykA1A#.UyQCD4V788k

author: EEVblog
author_rank: Unknown
timestamp: March 15, 2014, 07:34:44 am
content: Quote from: AznGothic on March 14, 2014, 11:17:06 amYou can't pay that and expect anything decent.

author: AznGothic
author_rank: Contributor
timestamp: March 15, 2014, 07:55:00 am
content: Quote from: EEVblog on March 15, 2014, 07:24:23 amQuote from: EEVblog on March 15, 2014, 07:34:44 amI can not afford a $200 price tag. I explained that several times in my posts. And a PC based scope would still be portable with a laptop. Either way, I asked for advice on a portable scope that is PC based OR hand held. I don't need it to do any fancy tricks and I plan on buying a better one in the future. But for now I just need advice on which one for around $100 would get me by to do what I need it to do. And the only thing I need it to do right now is show me when the peak of the sine wave is getting clipped as I'm turning the gain up so that I don't turn the gain up to high.

author: Mark_O
author_rank: Frequent Contributor
timestamp: March 15, 2014, 10:25:53 am
content: Quote from: AznGothic on March 14, 2014, 08:37:23 pmNo, Hantek is not made by Sainsmart.QuoteIt's pretty simple really. It's just adjustable sensitivity. For some things, you need to see small signals, so you'd go to a lower setting. For your needs, you're looking at relatively high voltages, so you'd select the higher setting (less sensitive), and use a 10x setting on the probes provided. That should give you enough headroom for what you're doing.QuoteSorry, that was inappropriate of me. FFT is just a fancy name for looking at all the individual frequencies that make up a signal, stretched out over a spectrum chart. I suspect you've seen frequency-response charts, that show how flat or variable the response of an audio component is. This is similar, because it shows all the frequencies that are present. If your test tone is a pure sine wave, then the frequency chart (FFT) would be a flat horizontal line at 0 level, with just one vertical spike, at the test frequency. But as you turn up the volume, distortion will rise. Distortion is any frequency in the output that wasn't in the input. So you will see small blips start to appear on the frequency chart, at multiples of your input sine wave frequency. (And those multiples are 'harmonics'.) Those will be noticeable much sooner than the top of the sine wave will start to look clipped.QuoteWell, clipping is a really 'hard' distortion, where the maximum drive is reached, and exceeded. The amp just can't put out any more voltage, so the top of the sines go flat. Certainly there will be plenty of 'spurious harmonics' (other frequencies you don't want) at that point, but there will be some even before you reach that point.The technical term for the distortion of the rise/fall of the wave is slew-rate. Slew rate limiting usually becomes an issue at higher frequencies. I.e., you may be able to put out a certain voltage at a lower frequency, but as you go higher, the voltage can't change fast enough, and the shape of the sine curve won't be maintained. And eventually you can no longer reach the desired peak value at all. Slew-rate limiting will be even harder to see initially, just by looking at a sine wave shape, though since it's related to the bandwidth of the amplifier, you'll eventually notice it as reduced amplitude (height) of the sine wave. I.e., it will shrink.The question there is determining at what point do you back off and say, "that's too much limiting?". High frequencies are not emitted at as high a level as low ones... if they were, tweeters would be blown out all the time. You sure don't want to run that test at full-rated power levels.The good news is that all of these can be easily seen on the FFT graph I mentioned.

author: VK5RC
author_rank: Unknown
timestamp: March 15, 2014, 10:33:05 am
content: If you are only doing audio and have a PC (esp if it has a decent sound card) and $ is a bit tight right now, how about an attenuator at 8 or 4 ohms impedance (or whatever is needed), and stick the appropriate level up a good sound card and let the PC and a freeware "soft oscilloscope" do the rest?Clearly a dedicated instrument will do a lot better.

author: EEVblog
author_rank: Unknown
timestamp: March 15, 2014, 11:04:51 am
content: Quote from: AznGothic on March 15, 2014, 07:55:00 amThe PC based one will just be a complete PITA for this application. I'm assuming you need to actually do this inside the car?, if so the PC option is just too fiddly, forget that option IMO. Hand Held is the only way to go - it's instant on, rugged, small, convenient, battery last much much longer etc.QuoteAt that price point you are down in the toy category, they will all be various levels of crap, so it doesn't matter. The DSO nano, or this seems to be the only option around that price point:http://www.ebay.com.au/itm/MINI-OSCILLOSCOPE-HANDHELD-DIGITAL-SCOPEMETER-POCKET-SIZE-25MHZ-MULTIMETER-EM125-/271233154203?pt=AU_B_I_Electrical_Test_Equipment&hash=item3f26c17c9bMy recommendation is spend the extra $100 and get the Uni-T meter or this:http://www.vellemanusa.com/products/view/?country=us&lang=enu&id=525377You run a car audio shop and can't afford the extra $100 for a decent convenient tool? A good spanner will almost cost you that.

author: EEVblog
author_rank: Unknown
timestamp: March 15, 2014, 11:14:24 am
content: A cheaper option again:http://www.amazon.com/Velleman-PPS10-10MHz-PERSONAL-POCKET/dp/B000KK7FTO

author: commongrounder
author_rank: Frequent Contributor
timestamp: March 15, 2014, 01:16:58 pm
content: I've come to this conversation late, but I work with audio and have a VELLEMAN HPS140I in my small tool bag. It is around $100.00 street price, and is capable of displaying power output, in watts, at several selectable impedances. It has a 10x probe and can handle several thousand watts with no problem. There is no doubt the screen is small and pixelated, but it is clear enough to show the onset of clipping and allow you to read out a maximum power output quickly. It is single channel only, which I think is good, because, unless you have a scope with isolated inputs, a dual input scope could short the bridged outputs of two amp channels together with catastrophic results. Good Luck!

author: AznGothic
author_rank: Contributor
timestamp: March 15, 2014, 09:33:20 pm
content: Quote from: EEVblog on March 15, 2014, 11:04:51 amI'm always taking my laptop out to the cars I work on already to program car alarms to the vehicle. The only thing I hate about it is the touch pad mouse. I hate using touch pads. I'd rather have a mouse in my hand. Other then that, I find no inconvenience in it. I did see the Velleman HPS140 and considered it but no one had mentioned it until now. I hate how tiny the screen looks but I can probably deal with it until I can afford a better one. Like I said before, I really wanted to get the TPI 440 which is a handheld.Quote from: EEVblog on March 15, 2014, 11:04:51 amYes I run a car audio shop and can't afford the extra $100. I have a $300 drill and impact set, $200 automotive multimeter, $200 power probe, $100 router, $150 router table, hundreds of dollars worth of router bits, $100 circular saw, $200 butane soldering iron......you get the idea. All the tools in this business are expensive and in the hundreds. I racked up $2,500 in debt just on tools alone when I started this business. That doesn't include the loan payment for the building and land, inventory, utilities, credit card bills or advertising!....I have paid my $2,500 debt in tools down to $800. Once I'm done paying that off I will be purchasing a better oscilloscope but for now, approx $100 is all I can spare. I'm sorry we can't all be wealthy. Just because someone owns a business doesn't mean they are rich or can afford all the nicer stuff. I do live in the USA where no one can make up their mind on how to fix the economy. One president screws it up, the next one tries to fix it but congress just want to keep screwing it up. The tax laws changed this year and well this is tax season! Almost everybody got screwed over on taxes this year. Not to mention the new health care bill started this year as well which is screwing a lot of businesses over. So my apologies for not having pockets full of money but money doesn't grow on trees and I live in a country that just wants to fuck it all away! I work very hard just to stay in business!!And I have no clue what a spanner is!!Now if we're done talking about my financial situation, I'd like to get back to an oscilloscope I can afford. The Velleman HPS140 seems nice (aside from the tiny screen) and I found one on ebay up for bid. I've made arrangements to buy me more time in acquiring an oscilloscope so if I can win that bid around $100 I'll get that. If not, I'll get the Hantek that Mark_O suggested. And thank you Mark_O for all the info you gave me. It has been much appreciated.

author: pickle9000
author_rank: Super Contributor
timestamp: March 15, 2014, 10:32:28 pm
content: PC based scopes and code readers are very common in the automotive world. They range from fully integrated touch screen to a pc sitting on a cart and everything in between. A USB scope is perfectly normal in a garage situation.

author: kc9qvl
author_rank: Regular Contributor
timestamp: March 15, 2014, 10:41:59 pm
content: A spanner is a wrench.Here is a couple of photos from my hps140. 1000 hz and 500. Might help you decide if its something you want to pursue. You mentioned the screen size.The hps140 is usable to 5 Mhz before jitter and aliasing become a unworkable.

author: kc9qvl
author_rank: Regular Contributor
timestamp: March 15, 2014, 10:52:35 pm
content: He needs some TEF equipment.I've used smaart live software with a lexicon usb card and a dbx measurement mike.Over kill for car systems though.

author: AznGothic
author_rank: Contributor
timestamp: March 16, 2014, 03:13:41 am
content: Quote from: kc9qvl on March 15, 2014, 10:41:59 pmI've never heard it called a spanner before. We always say wrench, open end wrench, closed end wrench, boxed wrench....and a few other variations with the word wrench. Spanner is a new one for me.Thank you for the photo's. That actually doesn't look to bad. I imagined it would be harder to see the line detail or differences with how small it was but it's actually not to bad. Especially with the whole screen lit up like that. Does the screen stay lit like that at all times while in use? My multimeter has a blue back light but you have to press a button to turn it on and it only stays on for a few seconds. It's annoying that I can't turn the light on and leave it on.Quote from: pickle9000 on March 15, 2014, 10:32:28 pmThank you!Quote from: ErikTheNorwegian on March 15, 2014, 10:44:19 pmDon't know what I would need a noise generator for. For sine waves I have audio tracks for each individual frequency. From my understanding the Octave Analyzer is pretty much the same thing as the FFT feature for the Hantek? Did I get that right? As for measuring impedance, I have a very good multimeter with TrueRMS for that. My main concern is the lower frequencies since most of my box builds and installs are for SPL competitions.I'm liking the Velleman HPS140 more after seeing the photo's. Here's to hoping I win the auction on ebay. I know Velleman also makes some PC based oscilloscopes too that are around $100. Are those worth anything?

author: Lightages
author_rank: Unknown
timestamp: March 16, 2014, 04:32:01 am
content: If you are tight on money and can't afford much right now then forget the cheap osilloscope and use the computer/notebook with free software to use as a test instrument.http://www.sillanumsoft.org/for exampleBuy a cheap usb microphone:http://www.amazon.com/CAD-U37-Condenser-Recording-Microphone/dp/B001AIQGUO/ref=sr_1_4?ie=UTF8&qid=1394943537&sr=8-4&keywords=usb+microphoneand now you have an idea of the frequency response, and distortion of the system including the speakers. This is much better value for the price than just seeing if the amp is clipping.

author: EEVblog
author_rank: Unknown
timestamp: March 16, 2014, 04:49:25 am
content: Quote from: AznGothic on March 15, 2014, 09:33:20 pmFine, given that you don't like small screen (and that's all you'll veer get for $100 on a handheld), just buy whatever PC based USB scope you can afford, they are all pretty much the same for your purpose.

author: TMM
author_rank: Frequent Contributor
timestamp: March 16, 2014, 08:17:12 am
content: As someone who dabbles in car audio as a hobby, all the cheap 'pocket' DSOs suck. The interfaces are just downright frustrating to use and most of the time they don't store your last settings so you have to go through a >30second setup routine every time you get it out. They aren't usually very rugged either. The DSO Nano i had lasted all of about 30 uses until the probe jack got dodgy and the battery life became appauling. The probe jack is also some uncommon/proprietary type so if you don't like the standard probe (it's hardly optimal for car audio work) then you have to modify a probe... The cheapest portable scope i'd probably buy is the Uni-T UT81 and even that has a bit of a clumsy interface.PC based solutions fall into pretty much the same category - faffing about with a PC while working on a car is just very unergonomic imo.A second hand benchtop oscilloscope is far nicer and more efficient to use because you have dedicated knobs instead of having to browse through menus with push buttons and you won't lose your settings every time you power it down.$50 second hand benchtop analog oscilloscope + wheeled cart + mains extension lead + couple meter alligator clips or multimeter probes to BNC cable. Job done.If you need a generator add an old headunit + car battery to the cart and burn a CD full of sine waves.

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: March 17, 2014, 08:50:06 pm
content: This discussion kind of begs the question, this has to be a reasonably common 'want' for car audio installers. I know there are automotive-specific scopes, but they're much more expensive, comparable to low-end handheld electronics scopes. Seems like you could make a reasonably cheap single-purpose audio diagnostics scope for 1 or 200 Vpp just to measure sonic quality at various points throughout an audio installation.

author: mainman
author_rank: Regular Contributor
timestamp: March 18, 2014, 06:24:36 am
content: Quote from: AznGothic on March 15, 2014, 09:33:20 pmOK dude, I am sure no one meant any offense. Sometimes I too am amazed over the deep pockets of a lot of members here. I mean so many here can just causally buy things such as a fluke 87 a $1300 Rigol spectrum analyzer or a 4 channel 200 MHZ Rigol DSO, good lord. I see videos of labs that have all these things in the background and wonder how can they afford that. In comparison I have to save up to buy my test equipment as I can not afford to buy any piece of test equipment over $80 at the drop of a hat. For example I desperately need a LCR meter badly but can't afford the $250 for the cheapest model that will meet my needs so I am saving up. Never buy the cheapest piece of crap based on the money you have on you right now, just save up.My first scope was actually one of those $100 nano, worse $100 I ever spent. Where I am getting is maybe you should save up and get a descent scope instead of what ever low end toy you can afford with your current funds at hand.The UT81B would be a good purchase for your needs.http://www.amazon.com/Uni-T-Handheld-Digital-Multimeter-UT-81B/dp/B008133N1Q

author: pickle9000
author_rank: Super Contributor
timestamp: March 18, 2014, 06:39:06 am
content: @AznGothicI'm a little curious, are you basically an autosound guy or are you interested in the electronics under the hood as well?

author: HP-ILnerd
author_rank: Frequent Contributor
timestamp: March 20, 2014, 06:13:29 am
content: I have actually managed to debug something in an impromptu setting with that Velleman pocket scope. It suffers a bit from the button interface, and the lone channel, but it is really super-portable. It was definitely better than nothing.That said, I have found the Rigol 1052e fits in a backpack like nothing, and is very light and compact. Out-of-budget in this case, I suppose, but having a real scope around can be a real boon.