azonenberg changed the topic of #scopehal to: libscopehal, libscopeprotocols, and glscopeclient development and testing |,, | Logs:
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<bvernoux> hello
<bvernoux> azonenberg, I was thinking to buy a nice AWG => Siglent-SDG6022X
<bvernoux> It is incredible for the price ;)
<bvernoux> and can be probably unlocked to 6052X as it is the same HW
<azonenberg> o/ bvernoux
<azonenberg> I've got a lot of stuff to work on
<azonenberg> i finished data collection on a sensepeek sp200 probe that a friend loaned me
<azonenberg> working on writing up a review
<bvernoux> ha nice
<bvernoux> I have the sensepeek sp200 ;)
<bvernoux> I have not tested them so far
<bvernoux> azonenberg, have you found a way to replace the senspeek sp200 by other scope probes ?
<azonenberg> bvernoux: the stock ground lead is pretty L-y
<azonenberg> if you solder a short length of solid copper wire to the shell, you can turn it into a 350+ MHz probe
<azonenberg> with the stock ground lead there's a big null at 150 MHz and huge peaking around 100 and 180
<azonenberg> time domain waveforms show a ton of ringing
<bvernoux> ha yes
<bvernoux> so it is not really a 200MHz scope probe ;)
<azonenberg> It did have -3 dB bandwidth around 200 MHz
<azonenberg> just wasn't flat between DC and there :p
<bvernoux> yes it can be an issue depending on measurement ...
<bvernoux> ha with tipground it is clearly better
<azonenberg> wait sorry
<azonenberg> the second 2 pics are with another improvised ground
<azonenberg> not the tip ground
<azonenberg> gimme a min to find that file
<bvernoux> this PCF200 TestFixture is interesting to test probes ;)
<bvernoux> It seems they have matched the connector transitions ...
<bvernoux> woo 555Euros for this test Fixture ;)
<azonenberg> It comes free if you buy a lecroy wavelink probe
<azonenberg> they use it for deskew compensation
<bvernoux> ha interesting
<azonenberg> This is the tip ground
<azonenberg> "myground" wasnt much better than stock
<bvernoux> the hacked tip ground seems to improve a lot
<azonenberg> Yes
<azonenberg> i plan to describe this in my review in hopes sensepeek offers a tip-side grounding option in the future
<bvernoux> yes it is will be a great upgrade
<bvernoux> I have 2 probes ;)
<bvernoux> my MSO5074 have more than 550MHz BW over 1Mohm ;)
<bvernoux> which is very nice
<bvernoux> I have checked that with my RFSigGen ;)
<bvernoux> so something better than 200MHz probes for senspeek is welcome ;)
<azonenberg> Yeah well try this mod
<azonenberg> it's easily reversable, just solder to the shield itself not the pcb
<azonenberg> just be careful how long you cut the wire
<azonenberg> you want it long enough that it makes contact after the pogo pin, but before the pogo bottoms out
<azonenberg> i would start with it the same length as the pogo in its extended state, then shorten by half a mm or so at a time until you're happy with the results
<bvernoux> I do not understand why they do not provide it
<bvernoux> as it is always better to have GND near probe pin
<azonenberg> well like i said, i intend to provide this data in my review and tag sensepeek in my tweet
<azonenberg> see what they have to say about it
<bvernoux> and not with this very long wire ;)
<bvernoux> of course for slow frequency < 100MHz it is not so important but it is great to push the probe to it's limit ;)
<bvernoux> I need to build a test fixture for probes
<bvernoux> I do not have anything
<azonenberg> I have two i use for different purposes
<bvernoux> I could reuse my TRL board (I shall finish to build it in fact the latest version)
<azonenberg> For higher speed stuff i prefer my own fixture which is a short length of GCPW on oshpark
<azonenberg> which has a sma at each end
<azonenberg> terminating in a 50 ohm load on one side and an open on the other
<bvernoux> yes it is interesting I have that on my TRL too
<azonenberg> i've characterized the transmission line itself fairly well in sonnet
<bvernoux> with 0402 capacitor on latest version
<azonenberg> and then use reference plane extension on the vna to remove the electrical length of the sma connector itself
<bvernoux> and I have the high precision 50Ohms res too ;)
<azonenberg> with that i've been able to de-embed the fixture quite well
<azonenberg> and get pretty accurate s-parameters
<azonenberg> sp200 with stock ground in blue vs tip ground in red
<azonenberg> impedance vs frequency to 500 MHz
<bvernoux> ha yes huge difference
<azonenberg> interesting to see just how *fast* it drops off. at 50 MHz it's only 300 ohms
<azonenberg> the AKL-PT1 is a better choice already, at 50 MHz
<bvernoux> so it shall work up to 500MHz ?
<azonenberg> Using the tip ground, i swept to 400 MHz with a sine generator
<bvernoux> yes but we cannot attach AKL-PT1 to senspeek stuff ;)
<azonenberg> and measured 420 mV p-p for a nominal 0 dBm signal
<azonenberg> No, that's what the AKL-PT4 is for
<bvernoux> the senspeek things is amazing to plug on signal on PCB
<bvernoux> I really like the weight of that things it is like magic
<bvernoux> how it move
<azonenberg> It will be an AKL-PT1 tip and attenuator with an M4 mounting stud and MMCX connector similar to what the sp200 uses
<bvernoux> ha nice
<bvernoux> to replace sp200 probes
<bvernoux> a bit like picoscope has done maybe ?
<bvernoux> as they have custom scope probe with sensepeek stuff
<azonenberg> they do? i thought they just resold sp200s
<azonenberg> blue = sp200 stock
<azonenberg> red = sp200 with tip ground
<bvernoux> the pink is the best ;)
<azonenberg> gray = lecroy pp023 passive probe
<azonenberg> blue-green = pico ta061
<azonenberg> green = lecroy zs1500 active probe
<azonenberg> pink = AKL-PT1
<bvernoux> ha nice so sp200 with tip ground is better than lecroy pp023
<azonenberg> At input loading, yes. The pp023 is flatter out to 500 MHz on S21
<bvernoux> do you plan to release all those files in the review ?
<azonenberg> This is the lecroy probe on the same signal using the spring ground
<azonenberg> slight overshoot but much flatter in general
<azonenberg> I will be including the measured s-parameters of the probe
<azonenberg> probably not the comparison chart but we'll see
<bvernoux> what peeksense has say when you have asked why they do not provide ground very close to signal pin ?
<bvernoux> Maybe they plan to sell a new probe with that feature ?
<bvernoux> much more expensive ;)
<azonenberg> i havent reached out to them yet
<bvernoux> ok
<bvernoux> do you have tested the limit of digital probes from senspeek ?
<bvernoux> the LA probes
<azonenberg> I have two sp200s, one modded with this ground lead and one stock
<azonenberg> and four sp10s
<azonenberg> i have so far not done any testing on the sp200s
<azonenberg> (also they're not mine and i have to give them back after i'm done testing)
<bvernoux> you want to say you have not done any testing on the sp10s ?
<bvernoux> and only tested sp200s
<azonenberg> Correct
<bvernoux> ok
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