Oscilloscope viability  - Page 1
Forum section: electronics / beginners

author: davelectronic
author_rank: Frequent Contributor
timestamp: March 03, 2019, 01:10:58 pm
content: It's been a long time coming, but now I could do with a oscilloscope for testing output noise and ripple of power supplys under load. Also buck and boost converters, I've seen this handy looking scope and wandered if it would be acceptable for the above uses. My budget is limited, I didn't want to go second hand as there's no guarantee it won't have a host of problems.Anyway, if someone could advise on this scope, I would appreciate that.Thanks for reading.Ps. Nearly forgot, it's the Velleman Handheld 40MHz Scope with USBShould have mentioned, it's primarily for testing output power supply ripple. And not so much for repair use.If that scope above isn't suitable, any suggestions on a scope for the same use with in a £250 To £350 budget.Thanks again.

author: rstofer
author_rank: Super Contributor
timestamp: March 03, 2019, 05:12:15 pm
content: https://www.amazon.co.uk/Rigol-DS1054Z-RIGOL-DIGITAL-OSZILLOSKOP/dp/B01LNY8CL0There are few decent scopes in your price range. The DS1054Z is quite popular and the Siglent SDS 1x04 entries are coming along but they cost more when compared 4 channels versus 4 channels. If I were looking for another scope, I might buy the SDS 1104 and unlock it to 200 MHz. The DS1054 can be unlocked to 100 MHz, details elsewhere.We have this discussion every week, you might try the Search feature or look over in the Test Equipment forum.

author: ebastler
author_rank: Super Contributor
timestamp: March 03, 2019, 05:22:54 pm
content: I agree with rstofer; if your budget covers the scopes he mentioned, they are much better choices.At what price was the HPS50 offered to you? If it is anywhere near to the budget range you indicated, run away screaming and avoid that seller in the future. The HPS50 isverylimited in comparison with the scopes rstofer mentioned -- bandwidth, sampling rate, and sensitivity are much worse, making it almost a toy by today's standards. An it is a discontinued model. Still available new for 170 Euro (150 GBP).

author: davelectronic
author_rank: Frequent Contributor
timestamp: March 03, 2019, 06:51:34 pm
content: Thanks for the replys. I will certainly look at the scopes you've mentioned, the HPS50 I can get for about £200 or just over that. I figured it was limited in its function to some extent, so will certainly look up your recommendations. I didn't want second hand as if it has issues, i doubt i have the ability to repair one. But it is really for testing outputs from power supply, or DC to DC converters.

author: ebastler
author_rank: Super Contributor
timestamp: March 03, 2019, 08:19:42 pm
content: The DS1054Z should be within your budget.E.g. 380 EUR (325 GBP) here, with free shipping in the EU:https://www.batronix.com/shop/oscilloscopes/Rigol-DS1054Z.htmlThe Siglents might be pushing your limit, unless you forego the 4 channels.Batronix has them as well. (As do other vendors, of course.)

author: rstofer
author_rank: Super Contributor
timestamp: March 03, 2019, 08:27:25 pm
content: Quote from: davelectronic on March 03, 2019, 06:51:34 pmIf you plan to work on DC to DC converters at higher voltages, you will probably want to look into differential probes (expensive) and, at least, x100 probes. If you're looking at low voltages, no problem.Watch Dave's video on "How Not To Blow Up Your Scope". That pesky ground strap is a real issue as it brings earth ground along wherever it goes.

author: Gyro
author_rank: Super Contributor
timestamp: March 03, 2019, 08:41:45 pm
content: The Velleman looks pretty poor value at that - monochrome lcd and single channel. It's only 12MHz bandwidth by the way - the 40MHz is actually 40M sps (samples per second).If you're looking for the same USB galvanic isolation and breaking ground loops then you could look at the Owon VDS1022I, it's less than half the price (£70 on ebay UK) and USB only but is 25MHz bandwidth and 100Msps and 2 channel.If your budget allows it then you should almost certainly go for one of the bench scopes previously mentioned but I though I'd throw it in as a superior option to the Velleman.EDIT: Not suggesting the USB isolation for Mains level circuits!

author: davelectronic
author_rank: Frequent Contributor
timestamp: March 04, 2019, 01:29:45 pm
content: The Rigol DS1054Z would be right at the limit of my budget, but suppose you get what you pay for. It does look like a very accomplished scope. The Owon looks like a pc usb type of scope. I would prefer an Amazon purchase, as it's a large purchase value, and would want cover for at least 12 months. I can see the Vellman isn't much more than a gadget really, I've gone through some Amazon ratings to see what's worth the money in terms of quality. I can see my budget is at the low end, but I like hacking IT psu's and server units, also hp and dell power bricks. I mostly want to see the output noise of these hacked psu's under load conditions. What my main intended use for these is to see if it's practical to use these units to power RF equipment, mostly linear amplifier and transceivers.I have watched Dave's measure ripple current video, but not the "how not to blow your scope up" yet. I will try and watch that video later today. The brand Hantek shows a couple of scopes on Amazon, one is 100mhz the other 200mhz but I'm unsure of the quality of these scopes. If I can find the Rigol you mention above I will go for that. It certainly looks like a very good quality unit.

author: AndyC_772
author_rank: Super Contributor
timestamp: March 04, 2019, 01:37:36 pm
content: Probes, probes, probes...!You mention that you're using the scope to measue the ripple and noise on a PSU under load, and this is a very difficult thing to do correctly and accurately without some experience with scope probes and their limitations. (It's something I've used as a practical test as part of an EE job interview, very few people got it right).The main problems are common mode noise and RF pick-up, and these issues can be reduced (not entirely eliminated) by choosing a probe which allows you to make a very short ground connection between the probe and the UUT. Typically this involves removing the ground wire with the croc clip, and making a connection instead using a grounded sleeve which the probe should have right next to the tip.Hint: always try probing the exact point where you make your GND connection to the UUT. In theory, of course, this shoud always measure 0V exactly, but it won't. Remember at the very least to subtract whatever ripple and noise you measure at the GND point from whatever you measure on the supply itself.If you don't probe correctly, it's very, *very* easy to make a noise measurement which is wildly inaccurate and incredibly misleading.

author: ebastler
author_rank: Super Contributor
timestamp: March 04, 2019, 02:34:06 pm
content: Quote from: davelectronic on March 04, 2019, 01:29:45 pmAre you buying this for a business or for personal use? If it's for personal use, you should be covered by the EU consumer warranty terms.In Germany that means 24 months warranty, although in the latter part of the term the buyer has to prove that it's a valid warranty claim. (I.e. failure is due to a defect/design weakness that was already inherent at the time of purchase. But reputable vendors like Batronix would only use this clause in drastic cases, e.g. when you present a scope with mechanical damage.) I believe it's the same for UK consumers? (Quick, buy it before Brexit!)

author: davelectronic
author_rank: Frequent Contributor
timestamp: March 05, 2019, 12:20:13 pm
content: It's for hobby use, and mainly to look at power supply noise and ripple. And only because some psu smps that is, are unsuitable for powering RF radio and related equipment. Up until now I've just tried moded IT including server units to see if they cause interference. A closer look at the output under load with a scope would be very useful. Yes I've seen Dave's video on how to measure output noise and ripple, and where his probe lead picks up noise from his led lighting. So that was very informative before I attempt this procedure.As I only plan to use the scope for looking at output noise, I'm unsure on the lowest mhz scope that will do this procedure. I have very little spare space, so a compact scope would be ideal, something I could pack away between uses.

author: AndyC_772
author_rank: Super Contributor
timestamp: March 05, 2019, 02:31:46 pm
content: Switched mode power supplies tend to produce the worst of their emissions in the form of fairly broad band noise in the 10-50 MHz region, so a 100 MHz scope will show you most of what's there to see. You may want to look at a scope with FFT capability too, if your main interest is in the frequency domain.

author: davelectronic
author_rank: Frequent Contributor
timestamp: March 06, 2019, 12:25:21 pm
content: Yes that's it really, what frequency is any noise coming from these hacked psu units under load. Anything that causes problems with RF equipment is of no use for my purpose. Unless additional filter network can attenuate the noise that is undesirable. It's not knowing the what the output noise is, under load that makes using such power supply possibly undesirable. Knowing the worst case noise scenario would be a great help in knowing if it's worth perusing a moded psu for RF uses.

author: rstofer
author_rank: Super Contributor
timestamp: March 07, 2019, 02:02:58 am
content: With the 100 MHz unlocking of the DS1054Z, you will be able to faithfully reproduce a 100 MHz sine wave. But you will be able to see 'trash' well above that frequency. In fact, the unlocked 100 MHz turns out to be 130 MHz before the trace goes -3dB down. Tested by others...That still wouldn't prevent you from seeing 'something' at a couple of hundred MHz or more. 300 MHz probes might help. 50 MHz probes won't help!Things get pricey when you move beyond 100 MHz. The Siglent SDS 1204X-E is nearly $800 for a 4 channel 200 MHz scope. I have read that the 100 MHz version, the SDS 1104X-E can be unlocked to become the 200 MHz version. Details over in the Test Equipment forum. The 1104X-E is only slightly more money than the DS1054Z but is probably outside your desired price range.

author: stj
author_rank: Super Contributor
timestamp: March 07, 2019, 06:39:23 pm
content: i saw a guy on utube testing the rigol, he got a good trace all the way up to about 350MHz!!!only downside, all the onscreen readings went to shit - but the trace was fine.this was using a signal generator that was probably putting out 1-3v, so i dont know how much the sensitivity dropped off though.

author: davelectronic
author_rank: Frequent Contributor
timestamp: March 08, 2019, 09:08:23 pm
content: Moding such an expensive piece of test gear is beyond my pay grade. Not only that I wouldn't won't to brick it. Looks like the best featured scope for the money.Thanks for all the suggestions and help.I'm in the UK and can only find one left on Amazon, probably gone now. And the Rigol web site, not sure if Joe public can purchase from there, or trade sales only.

author: ebastler
author_rank: Super Contributor
timestamp: March 08, 2019, 09:13:02 pm
content: Last time I checked, the UK was still in the EU. So this should work for you:Quote from: ebastler on March 03, 2019, 08:19:42 pmYou can't posssibly brick the scope by applying the unlock code for the options and higher bandwidth. The modification is easily removed, by a simple remote command. And, of course, you can always decide to leave the scope unmodified for now, until you feel more comfortable with it and have a real need for the advanced features.Go for it!

author: rstofer
author_rank: Super Contributor
timestamp: March 09, 2019, 02:21:15 am
content: Regardless of what the unlock code generator may say, you want to enter option code DSER. All of us had the same concerns, all of us just went ahead and did it anyway. It has worked for everybody. No scope was bricked - ever.

author: AndyC_772
author_rank: Super Contributor
timestamp: March 09, 2019, 08:39:30 am
content: If you want a Rigol, I can recommend Telonic as a supplier:https://www.telonic.co.uk/Rigol-s/1831.htm

author: davelectronic
author_rank: Frequent Contributor
timestamp: March 10, 2019, 11:19:28 am
content: Thank you for the link. Amazon have the Rigol back in stock now, at £375 pounds. It's an expensive purchase, but looks every bit worth the outlay.Thanks again for all the help and advice.