Oscilloscope suggestion?

[Behemot]

Hi guys

Sooner today, after blowing up my freshly upgraded crappy PSU, I decided it's bloody time to finally do my passive PSU load tester. That means I will hopefully join the VIP club of people doing PSU reviews soon too

Just one thing besides forcipate multimeter (easiest solution for measuring current I think and precise enough) I need is some oscilloscope. I have no knowledge in this area. Could you suggest me something usable in the ~100-200 euro range, preferably from here in Czech republic? If there is anything like that. I guess I would go directly for digital one with possible USB connectivity for exporting fancy graphs

[mariushm]

Re: Oscilloscope suggestion?

The cheapest I know of (when it comes to new, with warranty, and decent specs, with cheap shipping etc) is the Rigol DS1052E.
Batronix has them in Germany or Belgium, I forget now where they are exactly:

http://www.batronix.com/shop/oscillo...lloscopes.html

I bought one from them and arrived in a few days well packed, no problems.

Anyway, the scope would be good for measuring SOME things but if you want to do proper reviews you'd need a load (or more), which aren't quite cheap. Just a multimeter (or several) won't be enough.

[Behemot]

Re: Oscilloscope suggestion?

As I said, I am currently working on my own load. Passive load for the beginning - lots of resistors and halogen lamps for +12 V (they are great, few % of energy is transfered to light instead of heat ).

As for measuring than, I count on usual multimeter for voltage and forcipate multimeter for current. I hope thats the right english term, I mean this thing:


I think it is great, I can close in all cables of the voltage I want to measure, or one after other. It is additive. Position of the wires inside does not matter (at least something did the school gave me ). Yes, there are gonna be some fluctuations between the moments I will measure voltage and current, but really, would that be that dramatic? More than fractions of percent?

You know, here in Czech republic, nobody is doing even such basic reviews which could even be called reviews for many years on regulr basis. From time to tiem there is one, often with questionable quality, and than nothing in whoel country for another two years. I mean, looking inside, loading it around 100 % of its rated power, measuring efficiency. I do not need it to be professionaly accurate, +- few % is not anything drastic compared to NO reviews arround. You feel me?

[budm]

Re: Oscilloscope suggestion?

Clamp-on meter. Can it do DC current through the Clamp-on or you have to use the probe connector for DC current reading.

[c_hegge]

Re: Oscilloscope suggestion?

I use an EasySync/USB Instruments DS1M12 Stingray. It's the same scope as HardwareSecrets use. It's been fine so far.

[Behemot]

Re: Oscilloscope suggestion?

Clamp-on meter. Can it do DC current through the Clamp-on or you have to use the probe connector for DC current reading.

Haven't bought one yet, but sure, I want to buy AC/DC current/voltage. But I have the feeling even the cheapest do this.

[mariushm]

Re: Oscilloscope suggestion?

I forget to say a Kill-A-Watt type of energy monitor would be useful.

I bought this one from eBay a while ago: http://www.amazon.co.uk/Ecosaver-Ene.../dp/B00147F48Q

It's good, accurate, but this particular model doesn't compute the power factor correction. Other models do - it's worth searching for one that does.

I doubt a clamp-on meter would be accurate enough to determine efficiency and other things worth having in a review.

There's a constant current load circuit advertised initially by Dave from eevblog and later improved by others:

http://www.eevblog.com/2010/08/01/ee...ttery-testing/
http://www.sleepyrobot.com/?cat=7
http://mjlorton.com/forum/index.php?...29.msg92#msg92
http://www.youtube.com/watch?v=WSQeZdkbquI&feature=plcp (this one is probably the best designed yet still simple)

which allows you to finely adjust the current sucked within some limits.. up to around 4-5 amps. might be able to do more by putting several fets in parallel.

This circuit would make more sense compared to resistors and halogen lamps, you'd simply be able to build several and move them around to the rails you want, 5 , 3.3, 12 .. do crossover etc

[tom66]

Re: Oscilloscope suggestion?

I stand by Rigol DS1052E/DS1102E. The USB port lets you generate output pictures like this, and it's a dedicated instrument, so you can keep it away from your computer.

Third one shows the AC line current drawn by a power supply with a faulty PFC circuit. I used a Taewhatrans TS-10L current clamp. I have about 120 of the things at home. If anyone needs one, let me know.

[Behemot]

Re: Oscilloscope suggestion?

I have Voltcraft Energy Monitor 3000 which measures Cos phi.

As for load, I think it's fine, I gave that a thorough thought. I will of course add active load (transistors) later, but as for now I am good with passive load.

Load on -12 V will be achieved by industrial Papst fan working on potencial between -12 and +5 V. This fan with it's incredible airflow will cool down both resistors and halogen lamps, so they will keep their parameters within tight tollerance as their temperature will be more or less constant after some time. Every single resistor and lamp will have it's separate switch so I will be able to effectivelly select the load I will want on every rail. Including crossload. As for lamps, as I already said in other threads, they will have NTC before them eliminating current spikes to practically none.

Don't really see any problem here. As for clamp-on meter, why should not they be precise enough? Just gave it a view, they have accuracy arround +-3 %. I think that is good enough?

[tom66]

Re: Oscilloscope suggestion?

If you need greater resolution, then run two or three turns through the clamp; the current will be measured two/three times greater so you can read off smaller currents.

[Behemot]

Re: Oscilloscope suggestion?

Most meters which I can use have lower interval from 0,01 to 40 A so I think that would be enough, but thanks I would like to measure directly on ATX/peripheral cables so I guess I won't have enough of wire to round it three times anyway Just was thinking that there may be a slight problem with flexed cables. Hm, gonna have to cut the flexing I guess

[Kiriakos GR]

Re: Oscilloscope suggestion?

For reliable measurements with a clamp meter it needs to be industrial type and fast.

UNI-T is not famous about fast sampling.
My opinion is that you can do allot more with a Brymen BM189, but it is a product at 130EUR range, and not a generic hobby item.

About detecting ripple with a DSO you need something at 50MHz with a high resolution display.
The low end scopes does not come with higher resolution than 400x300.

It is probably best to get an used analog, at list you will not be limited from the screen of it.

[Behemot]

Re: Oscilloscope suggestion?

Been thinking bout Voltcraft VC-521…but that Brymen is not so much expensive, it's 1700 vs. 2400 CZK. On the other hand, is it that much better? VC-521 has 2,5 % on 40 A range, thats +-1 A. BM189 has 2,2 % on 60 A range, thats +-1,32 A. On the other hand BM189 can measure capacitance up to 2000 uF, I can use that too.

[budm]

Re: Oscilloscope suggestion?

*
Wrong post.

[Behemot]

Re: Oscilloscope suggestion?

What's that?

[MDOC]

Re: Oscilloscope suggestion?

I forget to say a Kill-A-Watt type of energy monitor would be useful.

I bought this one from eBay a while ago: http://www.amazon.co.uk/Ecosaver-Ene.../dp/B00147F48Q

It's good, accurate, but this particular model doesn't compute the power factor correction. Other models do - it's worth searching for one that does.

I have a Kill-A-Watt model P4400; power factor is among its measurement functions. https://cdn.badcaps-static.com/pdfs/...c975b7fdf7.pdf

edit: oops, max AC voltage: 125V, and the socket isn't for European countries

[ben7]

Re: Oscilloscope suggestion?

I am also looking for a beginner 'scope.

My Mother has a few friends that work at sciencey places, she will contact them and see if they have any old equipment.

If they don't I will be looking for a new scope, max budget of $300. Would like to have a digital one actually to take 'snapshots' of waveforms though

@tom66: Is it possible to make your own current clamp, with one of those clamp-on cable choke thingies?

(sorry if I am partially hijacking your thread behemot!)

[tom66]

Re: Oscilloscope suggestion?

Yeah, the current transformers convert the primary ac current into a secondary ac current with a ratio of 1:3000 (so the output is 3000x smaller.) Connect a 3kohm resistor across the output and get an output scale of 1V/amp. The maximum output voltage is about 7V (internal zener diode), so use a 300 ohm resistor to get 0.1V/amp. Max primary current is 85A continuous, 100A peak. They have a useful bandwidth of at least 20-30kHz so you can even see a limited amount of radiated EMI (and figure out how good the line filter is.)

[Behemot]

Re: Oscilloscope suggestion?

Bloody hell, loader is 95 % finished (will just add some halogen sockets, one resistor, couple switches, molexes for extra wires which I did nto have here and clean it up). Isn't it great when things go out as they are supposed?

[MDOC]

Re: Oscilloscope suggestion?

Think ebay and Tektronix.
http://www.ebay.com/itm/TEKTRONIX-TD...item3ccc3fe5c4

The above auction will have already ended by the time you get this, but it's a example of a simple o'scope and I think it has an output for the printer. Not sure, but I believe it does, and I've used it.