Products > Test Equipment
DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes
AVGresponding:
Calling something "compatible" implies a matching of capabilities.
When one finds oneself at the bottom of a deep hole, it is usually advisable to cease digging.
tautech:
--- Quote from: rogersstuart on December 30, 2021, 09:29:03 pm ---
--- Quote from: tautech on December 30, 2021, 09:01:41 pm ---
--- Quote from: rogersstuart on December 30, 2021, 08:31:10 pm ---@Johnny B Good
I was pondering this for a bit and decided to take a look at the original files. I think I know where the confusion came from.
In his (oz2cpu's) original design there was no ground fill on the top and bottom. If this had been made by simply omitting the inner layer gerber files then it would have not worked. When I edited the files I added a ground pour to the top and bottom to add a continuous ground throughout. If this was a microwave circuit then it would have not been appropriate to do so without net via shielding and recalculating the width of the traces. But for the frequencies involved I feel like it was appropriate and the coupling between the sides is insignificant compared to the input impedance. The only concern you should have is about the ribbon cable. But I do mention in the listing that it was designed for 120 ohm cable and that I did not include it, so I feel like I was being fair by mentioning that.
I don't want to get into an argument about international law here. Suffice it to say, I am well within my rights to reproduce a non-patented hardware design or take inspiration from one. Your concern should only be if I am attempting to defraud you, which I'm not. I have tested this and it works. That's all I can say to convince you. Really, all you had to do was test it and talk to me. I have had to work with people who have burned PCBs with a torch and want a refund. If you buy it and it doesn't work then deal with me that way. Starting with accusations is not productive between a buyer and a seller.
--- End quote ---
You're advertising: Siglent SPL2016 Compatible DIY Logic Probe
That it certainly isn't ! ! !
While it may fit a SDS2000X+ DSO and behave similar to SPL2016 it can in no way challenge the original performance.
Best you have a squiz at the specs here:
https://siglentna.com/wp-content/uploads/2021/05/Digital-Probe-Datasheet-V20E201912.pdf
FYI, original SPL2016 are supplied with 20 quality grabbers and not some POS grabber that falls of if you sneeze on it.
Offering a cheap low level substitute DIY MSO probe that fits a SDS2000X Plus would be well advised rather than mention of SPL2016.
--- End quote ---
Siglent SPL2016 Compatible DIY Logic Probe
Think please.
--- End quote ---
I think NOT !
This same PCI-e design is used by Tek, LeCroy, Rigol and probably others too, all with specs that your DIY version cannot duplicate.
Yes, it's a DIY MSO probe that fits SDS2000X+ models for the purpose of this thread but SPL2016 is in a totally different class.
rogersstuart:
--- Quote from: 2N3055 on December 30, 2021, 09:17:40 pm ---
--- Quote from: rogersstuart on December 30, 2021, 08:31:10 pm ---@Johnny B Good
I was pondering this for a bit and decided to take a look at the original files. I think I know where the confusion came from.
In his (oz2cpu's) original design there was no ground fill on the top and bottom. If this had been made by simply omitting the inner layer gerber files then it would have not worked. When I edited the files I added a ground pour to the top and bottom to add a continuous ground throughout. If this was a microwave circuit then it would have not been appropriate to do so without net via shielding and recalculating the width of the traces. But for the frequencies involved I feel like it was appropriate and the coupling between the sides is insignificant compared to the input impedance. The only concern you should have is about the ribbon cable. But I do mention in the listing that it was designed for 120 ohm cable and that I did not include it, so I feel like I was being fair by mentioning that.
I don't want to get into an argument about international law here. Suffice it to say, I am well within my rights to reproduce a non-patented hardware design or take inspiration from one. Your concern should only be if I am attempting to defraud you, which I'm not. I have tested this and it works. That's all I can say to convince you. Really, all you had to do was test it and talk to me. I have had to work with people who have burned PCBs with a torch and want a refund. If you buy it and it doesn't work then deal with me that way. Starting with accusations is not productive between a buyer and a seller.
--- End quote ---
There is no confusion. You took well made board and fiddled with it making it worse. Designer is an engineer and several others made the copy and verified design. It is good. Proven.
Removing inside ground planes completely destroyed AC return paths underneath the signals. Pouring ground on top did nothing except added DC return path. Sampling frequency and repetition frequency of signals on DUT doesn't matter. Only rise/fall times matter and even with Arduino pins you can get frequency spectra up to 1 GHz, believe it or not.. Raspberry PI has sub nanosecond edged on it's pins, it's even faster. This induces ground bounce, crosstalk and ringing. Thomas spent time designing this with good signal integrity, and did a decent job of it. There were some other attempts and they could see spurious pulses and noise that is not there. Not with oz2cpu though. It works well.
Designer doesn't mind you making boards and selling them for those who cannot be bothered to order them by themselves. All you needed to do was make them EXACTLY how they were designed, and somewhere in text give design credits to him... And they would work really well.. And I bet you that someone would mention it here as an good purchase option and you would get additional sales..
--- End quote ---
I understand the harmonics of a square wave. I think 1 GHz is a bit far out and this isn't a narrow bandpass filter or anything where a high degree of accuracy is needed. If you read the listing I mention that the original design was for 120 ohm cable and that I have included an alternative ribbon cable that worked for me. The component values are as the designer specified.
No one is reading and interpreting. There is just an onslaught of people making assumptions and not testing the reduced cost design. It was too expensive for my tastes to include the inner layers on that tiny board. I don't mention that the extra copper is or isn't included, say where I got it, or provide any implied warranty. Furthermore, I'm not advertising. Don't buy it. It takes up my time. I just like selling things on eBay. It gives me something to do sometimes.
With all that being said, I'm not the kind of guy who won't listen. If you buy one and see that it doesn't suit your needs then just say so. And that's it. It won't damage your scope. If you feel like the signal integrity is bad then what option do I have other than offer you a refund and investigate your claims?
rogersstuart:
--- Quote from: AVGresponding on December 30, 2021, 09:33:48 pm ---Calling something "compatible" implies a matching of capabilities.
When one finds oneself at the bottom of a deep hole, it is usually advisable to cease digging.
--- End quote ---
Compatible means that you can plug either into your scope and it will function. I think it's unreasonable to expect identical performance for $20 but if you do, well there are more than 7 billion people out there and everyone is free to have their own opinion.
Johnny B Good:
@rogersstuart
I was prompted by oz2cpu's sneaking suspicion that the main PCB may not have been an exact replica of his original 4 layer board and the great importance he places on it meeting this requirement, to verify whether it was a 4 layer board or not. You answered the question honestly and I thank for clarifying that point.
I sought further advice from oz2cpu before making any decision to cancel the order since your stated eBay policy is "no returns", denying me the opportunity to 'buy and try' as you've just suggested. Cancelling the purchase whilst this was still possible seemed the best option all round and I thank you for deferring to my cancellation request and the speedy refund.
Since the Belden ribbon cable undoubtedly accounts for most of the high levels of crosstalk shown by the graph you took the trouble to publish, it's impossible to say how much of a problem the lack of the inner groundplane shielding layers would be in this case.
Since oz2cpu had stressed the importance of a 4 layer PCB, I deferred to his judgement over your claim that this wasn't really that important after all. You may be right but there is no way to prove this, short of actually testing using twisted pair or coaxial cabling between the main PCB and the pods.
One way around this issue with your version of the main PCB, would be to wire up a pod using twisted pairs or coaxial cables and generate a new crosstalk graph for comparison against the Belden cable you're supplying as a courtesy to those with a more modest initial performance requirement.
Provided you've made it clear up front that the main PCB is only a two layer version of the original design and spell out your reasons for this cost cutting choice, backed up by the new graphical evidence obtained using twisted pair or coaxial cables, I should think you wouldn't have any further problems in this regard.
Supplying only a single 'starter pack' of test clip leads isn't such a bad idea since the quality and price of these test clips can vary considerably and it's best to economise here and allow the end user to make their own choice in the price/quality equation.
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