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Cheap probe for cheap scope?

As will shortly be obvious, I have no formal training in this stuff, but fool around with TI MSP430 and Arduino projects on occasion. And it would be nice to have a scope around to help figure out how things work or what's gone wrong.

In the latest episode of KnowHow (twit.tv/KH), Fr. Robert presents an inexpensive scope kit costing $23 from BangGood:

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The schematic for the DSO138 is in the Manual.

In addition, it looks like there's a more modern version currently on sale at about the same price:

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The schematic for the DSO150 is in a separate link about 1/4 way down the page.

Now of course these won't be much good with microwaves, but it looks like they might be fast enough to deal with anything I might do with an Arduino, including PWM and such.

My question concerns the probe. Both of these kits provide a probe that's BNC to alligator clips. I can't tell for sure, but I doubt there's anything in there except wire. However, both circuits have two trimmer caps that in theory provide for nice square waves.

What I would prefer to use is a "real", but cheap, oscilloscope probe with the little hook-on end, or you can remove that to get just a point. And the ground lead clips on right behind the lead. Probes like this (often referred to as P6100) are available in 1x/10x form, claiming to be 100 MHz, for about $6-7 each on Ebay, and on BangGood for that matter.

What I don't know is whether there's any reason a better probe wouldn't work with these scopes. The schematics are puzzling to me because the circuits involved for the different sensitivity paths are all connected in parallel even if only one circuit output is selected, and some of those circuits connect eventually to ground. But at these relatively slow speeds, does any of this matter? If I put the probe in 10X mode, which I think I would do most of the time, isn't it just a question of whether the trimmer cap on the probe and the trimmers on the board are of sufficient range to to get those square waves to show up as square? Or are there other potential incompatibilities that I should be concerned about. Of course I can just spend the $6 and find out, but, you know, what's the fun in that. Also, if it won't work, I'd like to be able to tell Robert why.

So I would appreciate any words of wisdom that might be forthcoming.

And by the way, for the price, aren't these scopes neat? Very goosey about BangGood though.

Reply to
Peabody
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A good treatment on scope probes:

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Reply to
John S

Spend a few hundred dollars and get a 60 MHz Rigol scope. It comes with probes.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

it has a 200 Khz sample rate, so it's not good for much above audio.

yeah it's just BNC to aligator clips. the black one goes to the shell the red to the pin.

a better probe would work, other than possibly giving easier connection there will be no benefit.

yeah.

it does what it says on the label.

I have brought lots of stuff from AliExpress, including 3 of those scopes. I had one with a bad inductor. I was able to source a replacement locally, so didn't try the conflict resolution process.

There's two different kits, one has the SMD resistors loose (in carrier strip), the other has them installed on the board.

If you don't like BangGood, you can probably get the same deal on Ebay or AliExpress.

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This email has not been checked by half-arsed antivirus software
Reply to
Jasen Betts

Here you go:

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Reply to
tom

I got one of those cheap scopes that plug in the USB port and the display wouldn't trigger real solid. Really sucked to look at PWM. By a real scope on Ebay, they're not much $.

Reply to
sdy

Thanks very much for your reply.

I think it would cover PWM, servos, steppers, rotary controllers, and other similar stuff you might do involving an Arduino GPIO port.

I don't expect any improvement in performance. I just don't want to make it worse. I ended up getting a 20 MHz probe, so we'll see.

AliExpress doesn't accept PayPal, and I'm reluctant to pay with a credit card.

Yes, I ordered a 15001K, which has the SMDs already installed, and includes a housing. So I only have to install the through-hole stuff.

I just hear a mixture of reports about Banggood. Great prices, but on shipping time and customer service, you just never know.

In the end I found US Ebay sources for the scope kit, the probe and the 9V power adapter, at slighly higher prices than BG, but with free shipping, so about the same in total, and probably a couple weeks faster delivery.

Then I ordered a 9V battery connector - to - 5.5 x 2.1 barrel connector in case I ever want to use it where there's no mains access, and the little TTL - to - USB translator board in case I ever need to update the firmware, both from China, but not needed anytime soon. Altogether it was $40 delivered.

If I made my living doing this, such a scope would of course be inadequate. But for hobby projects, I think the cost and performance are about right.

Reply to
Peabody

** Read it again - max sampling rate is 1MHz. 200kHz is the *analogue* bandwidth, plus it has 12bit resolution.

Not too shabby for the price.

.... Phil

Reply to
Phil Allison

I was going from memory. Thanks!

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This email has not been checked by half-arsed antivirus software
Reply to
Jasen Betts

I've seen one in action, the display is a bit glitchy but you get a reasonably useful tool for not much.

NT

Reply to
tabbypurr

I got this

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from AliExpress not long ago. I haven't tried it out at high frequencies but it does fine at audio freqs.

I have a few fixed 10x Tektronix probes but the single 1x/10x probe I had died after some 30 years of service and I ordered this one from AliExpress as a replacement. It comes with a detachable hook tip. At US$3.64 with free shipping, it's a steal.

Some caveats though: As with many cheap Chinese products, I wouldn't be surprised if the wire turned out to be rather flimsy and not very durable if it's not used with some care. And with free shipping, it may take up to several weeks to arrive.

Reply to
Pimpom

His voice gives me a headache. :(

--
Never piss off an Engineer! 

They don't get mad. 

They don't get even. 

They go for over unity! ;-)
Reply to
Michael A. Terrell

Lower your volume. :)

Reply to
John S

That only works, when I can no longer hear him. :(

--
Never piss off an Engineer! 

They don't get mad. 

They don't get even. 

They go for over unity! ;-)
Reply to
Michael A. Terrell

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