Cheap oscilloscope & other test equipment

[GARTHWILSON]

Dave Jones has a rant about oscilloscopes on his EEVBlog #86, and frankly, he's right. His basic message in this one is that cheap 'scopes like the DSO Nano are worthless; and after seeing his review of it, I totally agree! His recommendation--actually his pleading, after all the times he's been asked about the cheapie 'scopes--is that if you're on a tight budget, then get yourself a basic 20MHz dual-trace triggered oscilloscope which you can sometimes even get for free these days.

In his review of the Nano, this thing that claimed to have 40MHz analog bandwidth started having serious problems above 1MHz! It only had one input (you need at least two!), no separate trigger input, had a serious problem with input noise from a bad front end, it didn't let you adjust the trigger level while viewing the results at the same time so you could see what you're doing, and didn't even have an AC-coupling input option! It's a worthless toy. He's right to try to steer the newbie away from the frustration it would bring.

He has a video blog on setting up an electronics lab, at https://www.youtube.com/watch?v=R_PbjbRaO2E. I posted about it on the sparkfun forum in response to someone's question, and the OP said he didn't think he would need 90% of that stuff. But like Dave said near the end, a lot of that stuff gets accumulated slowly over the years. He discusses the very basics at the beginning though, and I agree with most of it. I've seen here where beginners really cause themselves a lot of trouble and frustration by not getting for example a good DMM and power supply like Dave talks about, and a basic 20MHz dual-trace, triggered analog oscilloscope. Without an oscilloscope, you're working in the dark. It's far more important than some of the things (like simulators) that beginners think they need.

[whartung]

I have an oscilloscope of some kind at home. I scavenged it from the office when they were clearing out a storage unit. It's just the scope as far as I recall, no leads. I assume it's reasonable quality. I have absolutely no idea how to use it. It's languishing in the garage at the moment.

I also have a nice (well it seemed nice when I bought it at the hardware store) DMM, it just happens to be dead for some reason. Even after replacing the batteries. Not sure what that's about either.

[ElEctric_EyE]

GARTHWILSON wrote:

...Without an oscilloscope, you're working in the dark...

I got a nice scope from EBAY awhile ago. It's a Tektronix 2440, but it came with crappy probes, not even Tek probes. It's worth the money to buy good probes too, that at least match the frequency of the scope. Anything I measure above 40MHz looks like a sinewave, but it still helps me out when I'm really stuck. Although, I know for my present work I'm missing seeing all the high frequency noise @~100MHz... I've still yet to upgrade because the probes are so expensive, but they're on my list of things to purchase very soon.

[BillO]

I have one of those cheap little DSO NANO scopes. For what I use it for, none of my other scopes are of practical use while it fits the bill just perfectly. I got it mainly to work with my son's off-road racing motorcycles in the field. It's just not practical to bring my big Tektronics or even my Unit-T DSO out into the woods. The capabilities of the little NANO scope are plenty for working with the frequencies found in the ignition and lighting systems in his bikes and it reproduces the waveforms with sufficient fidelity to make it far more than worthless.

Is it a replacement for the good bench scope. No way, but it's not useless.

[BillO]

BigDumbDinosaur wrote:

Interesting. 100 MHz is certainly good enough for experimenting with pretty fast circuits (10 MHz at least, assuming the 10:1 ratio). Funny thing is at first glance the 'scope almost looks like a microwave oven with a bunch of knobs on it.

It samples at 1GS/sec, so it's pretty good to close to 100mHz. I am really pleased with this scope for the price. It has performed beyond my expectations and you can't ask for more than that, from a personal perspective at least.

Actually, there is a little story behind this scope. That quirky behavior I mentioned before turned out to be a bad scope. I thought, since I bought it from a Chinese vendor off of eBay, I would be out of luck. I contacted the vendor anyway and they got the manufacturer involved. Between them and I, we determined the scope to be bricked. The vendor shipped me a new one without delay and paid for me to send the bad one back. You can bet I am absolutely delighted with that kind of customer service. The new scope, as I said, has turned out to be better than I originally expected. All in all, a great experience and a great deal for the money. The eBay vendor was infinitystore0001. You can trust them.

[BigDumbDinosaur]

BillO wrote:

Actually, there is a little story behind this scope. That quirky behavior I mentioned before turned out to be a bad scope. I thought, since I bought it from a Chinese vendor off of eBay, I would be out of luck. I contacted the vendor anyway and they got the manufacturer involved. Between them and I, we determined the scope to be bricked. The vendor shipped me a new one without delay and paid for me to send the bad one back. You can bet I am absolutely delighted with that kind of customer service. The new scope, as I said, has turned out to be better than I originally expected. All in all, a great experience and a great deal for the money. The eBay vendor was infinitystore0001. You can trust them.

They sound better than the average Chinese vendor. You lucked out, my friend.

[Tor]

GARTHWILSON wrote:

Dave Jones has a rant about oscilloscopes on his EEVBlog #86, and frankly, he's right. His basic message in this one is that cheap 'scopes like the DSO Nano are worthless; and after seeing his review of it,

To be fair, the review wasn't about the DSO Nano, it was another model (looks very different). The Nano doesn't claim to go above 1MHz, unlike that other scope. From what I can tell from the specs the Nano also has very different hardware inside.

But yes, I would take a good old 20MHz dual channel Tektronix before any of those, unless I for some reason really needed something that can be carried in a pocket.

-Tor

[GARTHWILSON]

Concerning the "& other test equipment" part of the topic title, my nearly-40-year-old Metex M-3650 DMM has been perfect until yesterday when the capacitance tester portion quit working.  I'm looking at Jameco's offerings (that's where I bought the Metex), at the Velleman DVM030 and DVM040 they offer for $66 and $90 respectively, which look good, particularly since I don't want to spend more than that, with the property tax and income tax bills this month, big insurance bills last month, and that my wife just spent $2200+ at the dentist.  If anyone has experience with these DMMs or other ones you think I should consider, please speak up.  Thanks.

[BillO]

How much accuracy and precision do you need?

Those cheap little component testers like the GM328A seem to be within the tolerance of most affordable capacitors.

https://www.aliexpress.com/item/1005004553677792.html

Might hold you over till things get better.

[GARTHWILSON]

Wow, that looks quite versatile; and if it breaks down quickly (like seemingly everything I've bought that's so cheap), it's no big loss.  It's nice that it measures inductors too, and FET gate threshold voltage.

[gilhad]

I have some similar for many years and it did not break yet (well, some character display wrong, i think it is Ohm, as block of random points, but it does not matter).

For some fast measurments it is good, even if I am not sure, how precise it is, it is consistent and with mainly digital circuits I do not care, if it is of by 0.2%, 1% or 5%.

(Well, "fast" - my take like second or two for each measurment, but I rarely measure more like 5 items at time - maybe "handy" will be better wording?)

[BillO]

GARTHWILSON wrote:

Wow, that looks quite versatile

They are. I actually have 3 of them. A T7, a T4 (which were free to me) and the afore mentioned GM328A. I'm not sure which is the chicken and which is the egg but they all work. The T4 is simplest and cheapest, the T7 is in a nice little case with a Lithium battery and charge port which makes it most convenient. However, I feel the GM328A is the best of them.

I modified my T7 to put a much bigger battery in it and banana sockets to use standard cables/probes with it.

They work and do a fair job of giving you a centerfield measurement.

[BillO]

Strange, I have had 3 notifications today about replies to this thread yet no replies have been made. Has the forum lost it's mind? Or is it me?

[Dr Jefyll]

BillO wrote:

Has the forum lost it's mind? Or is it me?

Possibly some spam got posted and then Garth removed it.

But it could at the same time also be true that you've lost your mind, Bill!

-- Jeff

[GARTHWILSON]

Dr Jefyll wrote:

Possibly some spam got posted and then Garth removed it.

I didn't this time, but I wonder if you'll get a notice if someone edits their older post.  I edit my old posts quite often, to fix links that went dead, clarify something, etc..