azonenberg changed the topic of #scopehal to: libscopehal, libscopeprotocols, and glscopeclient development and testing |,, | Logs:
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<azonenberg> So these resistors are actually quite a bit better controlled than the datasheet would have you think, lol
<lain> probably per-batch is very tight
<lain> but across batch is looser
<azonenberg> They're nominally +/- 0.1%
<azonenberg> So with 450 ohms that would give you +/- 0.45 ohms or 449.55 to 450.45 as the value of the resistor string
<azonenberg> biased toward the center assuming the distribution of each of the six resistors is independent
<azonenberg> You know what the actual resistance values i measure across the entire probe (tip to SMA, including solder joints and pcb traces?
<azonenberg> 450.23 to 450.39 ohms, average of 450.31, and a standard deviation of 44 MILLIOHMS
<azonenberg> That's +/- 80 milliohms of probe to probe variation, or +/- 0.017%
<azonenberg> That is *amazingly* consistent
<azonenberg> And that includes solder joint and pcb copper tolerances, not just the resistors
<azonenberg> although i imagine most is in the resistor
<azonenberg> Assuming the resistors themselves have a distribution centered at 450.00, that would mean the SMA + socket + trace + solder joints have around 30 milliohms of total resistance, which sounds reasonable
<azonenberg> (According to some google calculators (didnt bother with more accurate modeling) ~65mm of 0.31mm wide trace in 1 oz copper should actually be 100 milliohms, i wonder if the plating is reducing that?)
<azonenberg> here's the data from what i've measured to date
<azonenberg> DC resistance, rise/fall times, s21 at five points using the best ground, and -3 dB bandwidth using the best ground
<azonenberg> i have full s2p's of each probe with each ground accessory, this is just summary info
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<azonenberg> all of the probes from the kickstarter batch are assembled. One had a tip socket damaged during testing and needs to be replaced, i'm characterizing all of the others
<azonenberg> here's the data i've collected so far
<azonenberg> I'm doing the full professional edition workup on everything, even the standard edition ones for my backers, just to collect additional data on variability from unit to unit
<azonenberg> we were just commenting on how the nominal +/- 0.1% resistor string seems to have actual variability much less than that
<azonenberg> the overall DC resistance from tip socket to SMA is +/- 0.017% of the average measured value
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<electronic_eel> nice spreadsheet
<electronic_eel> is there any visual difference between s/n 0019 and the others?
<electronic_eel> it has a bit lower bw and higher risetime than the others, but the dcr is about the same as the others
<azonenberg> I was going to go back and visually inspect post characterization of everything
<azonenberg> if it's the soldering at the SMA, i can't see - they're already glued into enclosures
<azonenberg> but if it's the tip or resistor string i can see it
<azonenberg> i did observe that as well and it was interesting
<azonenberg> The numbers jump around a bit because i made 25 labels, printed 20 enclosures
<azonenberg> assigned them last to first because thats how the labels were printed
<azonenberg> then grabbed them out of the bin randomly to build 15 units
<azonenberg> I have full scope waveforms of the rising edge for each probe and full 2-port s-parameters, there's a lot more data than is in the sheet
<azonenberg> i'll be uploading raw data to starshipraider-caldata in an bit
<azonenberg> i also have to still rework s/n 0017 and collect input impedance measurements (not across a terminator)
<miek> got another part for the DIY cable rabbithole
<miek> the jig/heatsink part they use in that guide seems to be unobtainium though
<Degi> Which guide?
<azonenberg> 0018 is the worst yet, i might want to re-measure in case i had bad contact or something
<azonenberg> it's WAY worse than the rest
<Degi> Lol why is it a .pptx
<Degi> Whats an ECAL
<miek> it's an electronic calibration module. rather than connecting SOLT standards to all your vna ports, you connect an ecal and it switches through them all automatically
<Degi> Neat
<Degi> And that costs 10k?
<azonenberg> whats the main purpose, avoiding connector wear?
<azonenberg> i want one :p
<azonenberg> (i've known they existed for a while, just couldnt justify the budget lol
<miek> i think the main purpose is probably just making it easier/faster, but less wear is an advantage too
<miek> nice!
<azonenberg> the blue-green line at the very bottom is probe 18, i'm going to probably re-measure it to make sure it's not a fluke
<azonenberg> i'm debating calling that a defect and not shipping it
<azonenberg> Or being mean and giving it to somebody who ordered the student edition, who probably won't mind :p
<miek> yeah, it does stand out a bit
<azonenberg> seriously though if i ship it i'll have to extend my spec range quite a bit
<miek> ah i was gonna ask whether that met specs
<azonenberg> i'll try and rework it if it's just a badly soldered resistor or something
<azonenberg> The purpose of collecting this data is to write the spec :p
<miek> oh, lol
<azonenberg> I think i'm going to define that to fail
<azonenberg> then repair it if possible
<miek> i guess strictly it looks like it's still hitting -3dB at >2GHz, not much margin though
<azonenberg> it hits about 2.1
<azonenberg> but these probes are doing better than i thought, so i am planning to tighten up the spec range a bit so the min at -23.5 dB (3 dB down from the nominal -20.5) is actually something like 2.25 GHz
<Degi> Not 1.9?
<Degi> Ah nominal is -20.5
<azonenberg> Yeah
<azonenberg> Every other probe will pass that spec
<azonenberg> you can see in the second screenshot just how much 0018 is underperforming
<azonenberg> and then 0020 is an awesome grade-A probe top blue trace)
<azonenberg> the rest are all pretty repeatable
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<miek> azonenberg: btw, did you take a look at that EECS142 link from the other day? lab #1 & the video with Joel may be very interesting to you - it's all about measuring & modelling passive component parasitics
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<miek> i took apart one of those maury gauges to check how it works:
<monochroma> your stop watch is broken :<
<miek> :'(
<miek> "what's the time?" "time to throw away that sma cable"
<monochroma> lol
<monochroma> have you found many that are way out of spec?
<miek> not many, but some were
<miek> even had some with the pin protruding too far D:
<monochroma> cheap ones i hope
<miek> yup! i didn't really trust them before, so they haven't been connected to anything valuable
<miek> i just found a really bad one. initially i thought it was a positive (recessed pin) reading, but it was going an extra turn around the dial D:
<monochroma> o.o
<Degi> Hahaha
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<_whitenotifier-b> [scopehal] noopwafel synchronize pull request #213: Rigol: basic support for DS1000D/E -
<_whitenotifier-b> [scopehal] noopwafel commented on pull request #213: Rigol: basic support for DS1000D/E -
<noopwafel> it's actually pretty ok w/scopehal now as a debugging scope at low sample rates (8k). until it next randomly dies, that is.
<bvernoux> noopwafel, nice
<bvernoux> noopwafel, maybe I could try it on my old DS1102E ;)
<noopwafel> that's pretty much what I just tested it on now
<noopwafel> so it should .. sort of work? :P
<bvernoux> it work through USB ?
<noopwafel> yes
<bvernoux> ha great
<noopwafel> also rs232 :D
<bvernoux> hehe
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<Degi> TPS62135 can be used as inverting buck boost heh
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<electronic_eel> Degi: the TPS62135 is a buck. you can use most bucks as inverters. but how do you configure it as boost?
<Degi> Connect Vin to the Vin of the TPS, GND to the OUT of the TPS and the GND of the TPS gives you negative voltage
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<Degi> Though that limits it to 1 A and Vin + Vout = 17 V
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<electronic_eel> yes, that is the common re-use technique to use a buck as inverter. but you wrote "buck boost". how to get the boost part?
<Degi> Ah idk
<Degi> I mean it boosts to a negative rail?
<Degi> Well its inverting boost
<electronic_eel> ah, ok
<electronic_eel> I thought you found a way to create a non-inverting boost
<Degi> Hmh the temperature here makes my chocolate soft .-.
<Degi> Well you can make an unregulated boost
<electronic_eel> try the 99% cocoa one, that doesn't get soft that fast
<Degi> Hm yes, its milka luflee. Ill just put it in the freezer
<electronic_eel> urgh, milka. I don't like it at all
<Degi> Hm yes
<electronic_eel> from the bigger brands, try Hachez
<Degi> Does that cost much money, like where I could get actual food?
<Degi> I've eaten lindor spheres for a while, they were nice.
<electronic_eel> they are a bit over 2 EUR, don't think that is unreasonable
<Degi> Hm nice
<electronic_eel> now, how to build a chocolate boost, that boosts milka into nice chocolate? and I'd prefer if the process were regulated ;)
<Degi> Add MSG
<electronic_eel> MSG?
<Degi> Monosodium Glutamate
<azonenberg> lol
<azonenberg> a chocolate boost converter
<Degi> And coffeine
<electronic_eel> don't think I want that stuff in my choc
<azonenberg> now i'm imagining a toroidal inductor withe a chocolate core and... licorice? windings?
<Degi> Idk if you add some CNT's to the licorice and ferrite dust to the chocolate...
<electronic_eel> hehe chocolate core - need to put that into the freezer before use or it will melt
<Degi> High temperature chocolate
<Degi> Cross-linked
<electronic_eel> or is the danger to the core not melting, but being eaten?
<Degi> Cross-link the polymer
<azonenberg> i feel like polymerized chocolate wouldn't taste very good
<electronic_eel> azonenberg: did you crack open the case of the "bad" probe to see if the cause is visible?
<electronic_eel> or do you intend to keep it in a working state?
<azonenberg> Not yet sure
<azonenberg> i havent even looked at the part i can see yet
<azonenberg> busy w/ other stuff
<electronic_eel> ah, ok, no problem
<Degi> Oh cool, there's In100 solder from chipquik
<Degi> What solder wire would you recommend? Pb free from chipquik or is there better?
<azonenberg> Degi: chipquik sac305 has been my go-to for years
<azonenberg> with no clean flux
<azonenberg> lain, monochroma: so i kinda halfway have a 30 day trial of sonnet pro now
<Degi> Oh neat
<azonenberg> halfway, meaning there are problems with the license file
<Degi> awh
<azonenberg> i have the full solver but the editor isn't letting me use all the features
<azonenberg> effectively, until they straighten it out i can't use conformal mesh, >2 layers, >8 ports, s-parameter components, etc since those limitations are enforced in the editor
<azonenberg> but i can use the full 32-core solver with no cap on design size within those 2 layers
<electronic_eel> do you think it should work or does the limitation look intentional?
<azonenberg> It should work. I'm going back and forth with support now
<azonenberg> half the components still think they're on l2 basic, the other half think i'm on pro
<azonenberg> i think the license file was configured wrong
<azonenberg> Anyway I have a sim running right now that is a simplified version of the full AKL-PT1 probe with the resistors shorted out
<azonenberg> it's using 5GB of ram and is maxing out my workstation pretty nicely :p
<Degi> Neat
<azonenberg> so even gold would not be enough for this, however it's close enough to feasible that if i split it up into ~3 subsections, which should be doable, it would work
<azonenberg> and gold would let me model the actual resistor s-parameters
<azonenberg> Just a question of if i can come up with $8K ish before the end of the year as that's what it will cost me to upgrade
<azonenberg> and my support contract is up at the end of the year
<azonenberg> so my options are to do nothing and continue using basic but not have any upgrades or tech support
<azonenberg> pay a few hundred bucks to renew my support contract for basic
<azonenberg> pay around 4k to upgrade to silver, or pay around 8k to upgrade to gold
<Degi> Pay 4 k to a software dev to make OpenEMS usable?
<azonenberg> it would take a lot more than that
<azonenberg> i did the math already
<azonenberg> i would love openems to be usable but it's far enough from complete now that i'm much better off paying for a sonnet seat than hiring a dev to fix openems
<Degi> awwwh
<azonenberg> and i do not have the budget to pay for the amount of work openems actually needs to do what i want
<azonenberg> it would be IMO a kicad+cern level project
<azonenberg> major sopnsorship with multiple full time devs for years
<Degi> Hmh, I wonder how Sn96.5/Ag3.0/Cu0.5 comparess to the Sn96.3/Ag0.7/Cu03 of SAC305
<azonenberg> Hmm i'm not sure why you'd lower the silver content, cost? i've seen 3% Ag / 0.1% Cu which is supposed to be better for certain mechanical properties
<azonenberg> but 305 seems to be the industry standard right now
<Degi> Hmh mouser doesnt seem to have 305 from chipquik or at a reasonable price, I think the Ag3.0 should be fine...
<azonenberg> 305 is 3% Ag / 0.5% Cu
<Degi> Ugh now there are two wire gauges?
<azonenberg> My standard solder is around 0.5mm diameter but i have some 0.125mm that i use for precision work
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<Degi> Whats the difference between rosin and no-clean? Can no-clean still be cleaned with IPA or acetone?
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<miek> looks like that mouser listing is just wrong. digikey page & the datasheet has the right alloy
<miek> i don't use acetone on boards, but the no-clean i have cleans up just fine with IPA
<Degi> Does "CPT (Duty, customs, and taxes due at time of delivery)" mean that I have to pay cash to the delivery person?
<miek> yeah, or often they'll send you a letter demanding payment before they deliver
<azonenberg> miek: it depends on the carrier
<azonenberg> IME ups will pay the customs fees, deliver the box to your door
<azonenberg> then mail you a bill a week or two later
<azonenberg> sometimes a month later :p
<Degi> And "DDP (Duty and customs paid by Digi-Key)" means that I save a bunch of money?
<azonenberg> or that they charge you up front for it
<miek> or my latest fedex delivery from work had no bill sent, and then i got a debt collectors letter 5 months later
<azonenberg> lol
<azonenberg> Degi: re no clean, the difference is that no clean flux is safe to leave on the board after soldering
<Degi> haha
<Degi> Does rosin go bad?
<Degi> Is that the weird old device smell
<azonenberg> activated rosin fluxes need to be removed to avoid corroding the joints
<azonenberg> these are further divided into water washable or those that need a solvent to clean
<Degi> Oh so I pay the 10 $ vat myself then hmm
<azonenberg> No-clean flux can, but does not have to be, removed
<azonenberg> It also comes in water or solvent clean versions
<azonenberg> both the flux in my solder wire and my standalone flux are no-clean and come off nicely with ipa
<miek> if it's being couriered, you will almost never get away without paying the customs and such, so just go DDP for less hassle
<miek> and yeah, you will save money cause the courier won't stick an extra processing fee on
<azonenberg> So my giant sim is still running, but some interesting observations to date
<Degi> Okays ill order ddp then
<azonenberg> most notably that big roll-off at 2 GHz doesn't seem to be present
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<azonenberg> Which lends credence to the theory that it's the resistor array at fault
<Degi> Does UPS send an order number sometime
<Degi> *tracking
<miek> yeah, you'll always get a tracking number from digikey
<Degi> Will they send a mail? Since I ordered as guest
<miek> er, i dunno, i didn't know you could order as a guest on there o.o
<Bird|otherbox> Degi, they will send email if you provide them an email address
<Bird|otherbox> even if you don't create an account
<Bird|otherbox> (I've ordered countless things from DigiKey and still haven't bothered creating an account on their website yet)
<Degi> I have an ebay account and still dont bother using it... haha
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<azonenberg> Hmm interesting there does seem to be a smallish resonance in this board somewhere? still waiting on the sim
<azonenberg> yes with 32 cores it's still taking hours lol
<azonenberg> so far 11 frequencies at about six minutes each
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