<Degi>
Huh turns out a ultrasonic soldering iron can solder to glass really easily
<Degi>
The cables from that PDF look fun
<Degi>
The 8104 has 1 GHz bandwidth...
<Degi>
Anyways I have an idea for AC coupling, what if we instead of making DC offset with a DAC, when AC coupling is active we can LPF the input signal and apply the inverse of that with an OP amp as offset
<Degi>
That would still limit the input range to 2.5 V but we'd have 50 Ohm DC to 100 MHz
<azonenberg>
So have an analog mux on VIN_OFFSET?
<Degi>
yeh
<azonenberg>
and have it be DAC or LPF(input)?
<azonenberg>
we could use an active LPF
<Degi>
Hmmm
<azonenberg>
that also inverts
<azonenberg>
I guess the real question is how much we need something like that?
<Degi>
Better idea: Average n samples from ADC and adjust DC offset till said average is 0
<Degi>
We dont probably
<azonenberg>
honestly, i just don't see the use case for ac coupling scope inputs most of the time
<Degi>
We could add AC coupling in the probes maaybe if we make some with large input capacitances. Or maybe with a second op amp in there and a mux
<azonenberg>
you can buy SMA DC blocks off the shelf
<azonenberg>
If we need it
<azonenberg>
my point is more, at least for what i do, i almost never need it
<azonenberg>
i honestly cannot remember the last time i used ac coupling on a scope frontend
<Degi>
Wait why is a DC block rated for DC-6 GHz?
<azonenberg>
lol that sounds like an error in specs
<Degi>
Search "sma dc block" on ebay.com theyre all like that
<azonenberg>
The halfway decent ones specify min/max frequency
<miek>
also interesting that they just terminate one side of the diff output on that probe's amp. i feel like that's going to be the nice easy solution for an lmh3401 probe too
<azonenberg>
The BLK-89-S+ from minicircuits for example is rated for 0.01 dB typical insertion loss from 100 kHz - 100 MHz, then gradually increasing out to 8 GHz 0.5 dB
<azonenberg>
miek: yes i noticed that too
<azonenberg>
since almost no high bandwidth amplifiers actually have single ended outputs
<Degi>
Hm you mean for like a differential probe?
<Degi>
I mean yeah you can do that
<azonenberg>
Degi: i mean an active probe with single ended outputs
<azonenberg>
I definitely want to build a relatively inexpensive active differential probe at some point
<Degi>
Hmh maybe ill actually try that one design with the resistor capacitor when my scope arrives
<azonenberg>
"resistor divider probes good to maybe 2 GHz"
<azonenberg>
Pico would like to have a word with you...
<Degi>
Hmh maybe 500 MHz
<Degi>
Like with an op amp ofc
* azonenberg
looks at 9 GHz probe
<Degi>
Hmh Rigol has a power supply unit for the active probes..
<Degi>
Hmh tbh passive probes are kinda unusable above a few tens of MHz unless theyre resistive divider types...
<Degi>
Neat
<azonenberg>
They OEM basically all of pico's probes other than the picoconnect series
<azonenberg>
as well as all of lecroy's passive probes and their lower end active probes
<miek>
i'm very thankful for TSP's teardowns. one of his other probe teardowns made me realise that a broken probe i'd seen on ebay was very likely fixable, and that's how i got a 1.5GHz active probe for £100 :)
<azonenberg>
my lecroy zs1500 is a rebranded pmk tetris
<azonenberg>
unsurprisingly keysight uses their products too
<azonenberg>
those little blue capped plastic tubes of spare tips are pretty distinctive
<azonenberg>
also ooh digikey order came in. including some of these new SMA connectors
<azonenberg>
They probably will need to be glued. The fit is quite loose
<bvernoux>
yes
<bvernoux>
like for mine
<bvernoux>
it is the main issue with those SMA connectors
<azonenberg>
yeah but the fancy ones you screw on are $$$$
<bvernoux>
I was planning to do that today but weather was too bad and I do not want to do it in my lab with bad fume ;)
<bvernoux>
next step will be to buy a good fume filter for test inside my lab
<azonenberg>
bvernoux: i highly recommend the hakko fa-430
<bvernoux>
ha yes with an HEPA filter
<azonenberg>
You have your choice of HEPA or HEPA+activated carbon filter media IIRC
<azonenberg>
then a pre-filter that goes over the main to extend lifetime
<azonenberg>
although realistically they last a LONG time. I haven't even had to change a pre-filter yet
<azonenberg>
and i've left the thing on for hours by accident at least once because it's so quiet i can barely hear it over all the other fans in the lab
<bvernoux>
yes it seems great but a bit expensive > 600USD ;)
<azonenberg>
(the filter change reminder is based on counting tach pulses on the fan so it's RPM dependent)
<azonenberg>
It's not cheap. But absolutely worth it
<monochroma>
just need an off the shelf HEPA room filter system and some dryer vent hose to make one <$200 :P
<azonenberg>
The hakko hoses are *really* nice though
<azonenberg>
ESD plastic, not conductive enough to short stuff if you brush them up against it by accident
<azonenberg>
stiff enough to hold their shape
<azonenberg>
But still flexible
<azonenberg>
Can you do OK-ish for much less? Yes
<bvernoux>
yes it seems it is premium Fume Extractor
<azonenberg>
But if you can afford it, you're not wasting your money
<azonenberg>
And if you spend as many hours a day in the lab as i've been lately, it's worth it
<bvernoux>
the hard part is to find it near France ;)
<bvernoux>
because with COVID it take weeks to have something coming outside EU
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<Degi>
Stuff from china ships surprisingly quickly
<Degi>
10 filters for 102 €?
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