Products > Test Equipment
DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
oz2cpu:
milling combined with Vcut, no big deal, also looks like the connector edge is not sanded, in my STL file set, you find the sander tool
with this one you can sand at perfect angle and make the line straight, it is nearly impossible to do correctly without,
I tried, it looks bad
Johnny B Good:
He's even included the sanding tool (inluding a sheet of glass/sanding paper) which bodes well for the expected reply (fingers crossed) - see attached image.
oz2cpu:
super, happy sanding, and i really hope it is 4 layers
just a bit sad the layer identifier is performed wrong, so you cant see thru
I design pcb's for a living, so I am a bit crasy when it come to the layer identifiers, you know it is a nice way to confirm you got
somewhat close to what you ordered :-)
Johnny B Good:
Unfortunately, the answer I got was in the negative. It is, as you suspected, only a two layer board. He's claiming that with the board only being an inch long, the absence of the additional groundplanes should only matter if I were planning on analysing 4GHz clocked signals.
How small an issue it might be up to a 500MSa/s and a 3.3ns minimum pulse width limit as he claims is a bit too much of an unknown for me to answer so I'm asking you whether I should place any credence in his claim that this would be the case. I suspect your answer will be "No" and "just cancel the order."
I could PM copies of the email exchanges for you to peruse privately rather than here in a public forum if you like but, in short, his initial claim in the first email that
"This is the same thing you could make if you download the files from that topic."
(referring to this topic thread) has proved by his own admission in his 2nd reply, that he'd modified the board design beyond merely allowing it to be panelised by making it a two layer only PCB, thus breaking the terms of use of the licence you'd granted.
The thing is, despite this, it's an otherwise convenient way to acquire the parts for this project, even if it means ordering a main PCB from JLC. The unknown here being the additional cost this step would involve. :(
I'm probably better off cancelling the deal via the eBay resolution service since by his own admission, it hadn't been "as described".
rogersstuart:
Johnny, you're stressing a lot over a $20 kit and a 500 Ms/s logic analyzer. 250 MHz would be the Nyquist frequency. If this was a normal scope channel then you would have two points for for your sin(x)/x. 1/5 of that is equivalent to 100 MHz which is a good upper limit for signals that you might use with this. There may be a bandwidth spec somewhere. I'm not sure what it is. I can tell you that even the MSO5000 with twice the sample rate doesn't do well with logic signals of that frequency. And with your clocks not being synchronized, is that enough to result in what you're seeing not jittering around? I'm not an expert on how logic analyzers are designed. Maybe I'm wrong about why but it fits what I've seen. 25 MHz seems to be a good limit based on my testing. If you want the ground planes then you should also hunt down some nice 120 ohm coax to go with it which isn't easy or cheap. Also, these accusations aren't cool bro. I didn't say that it's 4 layers or lie about anything on eBay. I stumbled across this just like you and decided to sell the extra parts I had. I have to supply you with $5 of little probe clips, hand assembled boards (placing those passives hurts my back) baked in a modified toaster oven in my kitchen, cleaning in an ultrasonic cleaner, 3D printed parts that I blow hot air on to clean up wisps, sandpaper, ribbon cable, packaging, having a car, rent, and dealing with all the other stuff like responding to people (while I'm playing the new Final Fantasy video game) and testing things. I'm sure that's why the creator isn't selling them anymore. It's not worth the hassle. But I kind of like it. Someone from Japan ordered one yesterday which is cool. And I've sent one to Australia. So far, no complaints and I think that's 6 sold so far.
edit: I have been thinking about this. There isn't a lot said in the specification about the limitations of the logic analyzer. I was bothered by the fact that the signal jitters around a bit at higher frequency but I think it makes sense. If you have a 50 MHz signal, that's a 20 ns period. For a square wave at 50% duty cycle, half of that time will be high or low. One of those state will be around for 10 ns. With a 500 Ms/s sample rate we get a sample every 2ns. So, during this short 10ns window you would have only 5 samples. If things aren't perfectly aligned you would sometimes see quite a bit of jittering around.
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