#rC3 - Measuring radioactivity using low-cost silicon sensors

rc3 prerol music

Herald: All right, fellow creatures, to be
honest, I never thought that I would be

introducing a talk on measuring
radioactivity like ever in my life, but

then again, considering the world stage,
current state at large, it might be not

such a bad idea to be prepared for these
things. Right? And gladly, our next

speaker, Oliver Keller, is an expert in
detecting radioactive stuff. Oliver is a

physicist and works at one of the most
prominent nerd happy places. The CERN

since 2013 is also doing a PhD project
about novel instruments and experiments on

natural radioactivity at the University of
Geneva and to even more to add even more

C3 pizzazz. Oliver is active in the open
science community and passionate about

everything open source. All that sounds
really cool to me. So without further ado,

let's give a warm, virtual welcome to
Oliver and let's hear what he has to say

about measuring radioactivity with using
low cost silicon sensors. Oliver, the

stream is yours.

Oliver: Thanks. That was a very nice
introduction. I'm really happy to have the

chance to present here. I'm a member since
quite some years and this is my first CCC

talk, so I'm quite excited. Yeah, you can
follow me on Twitter or I'm also on

Mastodon, not so active, and most of my
stuff is on GitHub. OK, so what will we

talk about in this talk? I'll give you a
short overview, also about the

radioactivity, because yeah, it's a topic
with many different details and then we

will look at the detector more in detail
and how that works in terms of the physics

behind it and the electronics. And then
finally, we look at things that can be

measured, how the measurement actually
works, what are interesting objects to

check and how this relates to silicon
detectors being used at CERN. So the

project is on GitHub called DIY Particle
Detector. It's an electronic design, which

is open hardware. There's a wiki with lots
of further details for building and for

troubleshooting. There is a little web
browser tool I will show later, briefly,

and there are scripts to record and nicely
plot the measurements. Those scripts are

BSD-licensed and written in Python. There
are two variants of this detector. One is

called electron detector, the other one
alpha spectrometer. They use the same

circuit board, but one is using four
diodes, the other one one photodiode...

There's a small difference between them,
but in general it's pretty similar. But

the electron detector is much easier to
build and much easier to get started

using. Then you have complete part lists
and even a complete kit can be bought on

kitspace.org, which is an open hardware
community repository, and I really

recommend you to check it out. It's a
great community platform and everyone can

register their own GitHub project quite
easily. Now, this is a particle detector

in a tin box, so you can use the famous
Altoids tin box or something for Swiss

chocolate, for example. You can see it's
rather small, the board about the size of

a nine volt block battery. And then you
need, in addition, about 20 resistors,

capacitors and these silicon
diodes plus an operational amplifier,

which is this little chip here, this
little black chip here on the right side,

you can see is all old school large
components. This is on purpose, so it's

easy to soldier for complete electronic
beginners. And this by the way, this

picture is already one user of this
project who posted their own build on

Twitter. OK, so natural radioactivity. So
I would say it's a story of many

misconceptions. Let's imagine we are this
little stick figure here on the ground.

Below us we have uranium and thorium. We
also have Potassium-40 in the ground and

Potassium-40 is is pretty specific and
peculiar. It actually makes all of us a

little bit radioactive. Every human has
about 4000 to 5000 radioactive decays

every second because of the natural
potassium and natural potassium comes with

a radioactive isotope, which is just
everywhere, it's in bananas. But it's also

in us because we need it for our body
chemistry. It's really important and even

some of those decays are even
producing anti-matter. So how cool is

that? OK, so what would we be measuring on
the on ground? Well, there could be some

gamma rays or electrons. Those are from
beta-decays. Or from the Uranium, there is

one radionuclide appearing in the decay
chain, which is called Radon, and Radon is

actually a gas. So from the ground the
Radon can diffuse upwards and travel with

air and spread around. So it's a bit like
a vehicle for radioactivity from

the ground to spread to other places. And
that Radon would decay with alpha

particles producing electrons and beta-
decays and also gamma radiation further

down in the decay chain. So just to
recapitulate, I've said it already twice,

so alpha particles are actually helium
nuclei, so it's just two protons and two

neutrons and the electrons are missing.
And in beta decay basically one neutron is

transformed into a proton and an electron.
And there's also an electron-anti-neutrino

generated. But this is super hard to
measure. So we're not measuring those.

Mostly we will be measuring electrons from
beta-decays. That's why you see all these

little e's indicating betadecays. Ok, if
you would go to the hospital here on the

left side, we would probably find some x
rays from checking our bones or something

like this, or even gamma rays or alpha
particles being used in treatments or very

modern even proton beams are sometimes
generated for medical applications. Now,

here on the right side, if you go close to
a nuclear power plant, we probably measure

nothing unless there's a problem in this
case, most likely we would find some gamma

radiation. But only if there is a problem.
OK, and then actually that's not the whole

story. This is terrestrial radiation. But
we also have radiation coming from

upwards, showering down on us every
minute, and there's actually nothing we

can do against it. So protons are
accelerated from in the universe.

Basically, the biggest particle
accelerator nature has. And once they hit

our atmosphere they break apart into less
energetic particles and it's many of them.

So in the first stage there's lots of pions
generated and also neutrons. But neutrons

are really hard to measure, so I'll ignore
them for most of the talk. Then those

pions can decay into gamma rays and then
trigger a whole chain of positron electron

decays, which again create gamma rays and
so forth. And this goes actually the whole

way down to the earth. We will have a
little bit of that on the sea level.

And the other more known part of
atmospheric radiation is actually muons.

So some pions decay into muons, which is
kind of a heavy electron and also

neutrinos. But neutrinos are, again, very
hard to measure. So I'll ignore them for

most of this talk. And if you look here on
the right side on this altitude scale,

you'll see an airplane would be basically
traveling where most of the atmospheric

radiation is produced. And this is why if
you go on such an airplane, you have

actually several times more radiation
in there than here on earth. And, of

course, on the ground, it also depends
where you are. There are different amounts

of uranium and thorium in the ground and
this is just naturally there. So but it

depends on the geology, of course. OK, so
I've talked quite a bit about radiation,

and I'm saying I want to use silicon to
detect it. So what radiation exactly?

Maybe. Let's let's take a step back and
think about what we know maybe from

school. So we have this rainbow for
visible light. Right. This is in terms of

wavelength. We have 800 to 400 nanometers
spanning from the infrared/red area to all

the green to blue and into the violet. And
lower down those wavelengths or let's say

bigger millimeter waves, meter waves and
even kilometer, that would be radio waves,

radio frequencies for our digital
communication systems, wi-fi, mobile

devices and so forth. But I want to look
actually more towards the right because

that's what we are measuring with these
detectors. It's shorter wavelength, which

actually means higher energy. So on the
right side, we would be having ultraviolet

radiation, which is kind of at the border
to what we can measure. And these 800 to

400nm translate into 1.5 to 3 eV, which is
a unit that particle physicists really

prefer because it basically relates the
energy of an electron after it has been

accelerated by 1 Volt and makes it
much easier to work with nuclear

particle physics, because everything, all
the energy is always related to an

electron. And this energy, this formula
here is just a reminder that the

wavelengths can be always converted into
energy and it's inversely proportional. So

wavelength increases to the left and the
energy to right. And if you increase

energy more from from the visible range,
so let's say thousands of electron volts,

then we arrive here. Millions - mega
electron volts, even GeV. And there is now

a pretty important distinction between
those two areas, and that is the right one

is ionizing radiation and the left one is
non ionizing radiation. UV is a little bit

in the middle of that. So some parts of
the UV spectrum can be ionizing. It also

depends a lot on the material that the
radiation is interacting with. For these

detectors I'm talking about today and
alpha, beta, gamma radiation, this is all

ionizing, so some examples, lowest energy
on the lower spectrum would be x rays than

electrons, gamma rays from radioactive
nuclides that already talked about in the

previous slide, alpha particles, and that
muons from the atmosphere would be more on

the GeV range and so forth. And for these
higher energies, of course, you need

something like the LHC to accelerate
particles to really high energies. And

then you can even access the TeV regime.
OK, silicon diodes. What kind of silicon

diodes? I'm using in this project, low
local silicon pin diodes, one is called

BPW34 it's manufactured from Vishay or
Osram, costs about 50 cents. So that's what

I mean with low cost. There's another one
called BPX61 from Osram. It's quite a bit

more expensive. This is the lower one here
on the right. It has a metal case, which

is the main reason why it's more
expensive. But it's quite interesting

because that one we can use for the alpha
detector. If you look closely, there is a

glass on top, but we can remove that. We
have a sensitive area. So this chip is

roughly 7mm² large and it has a thickness,
a sensitive thickness of about 50

micrometer, which is not a lot. So it's
basically the half of the width of a human

hair. And in total, it's a really small,
sensitive volume. But it's it's enough to

measure something. And just as a reminder,
how much of gamma rays or X-rays we will

detect with this, not a lot because it's
high, energetic photon radiation kind

doesn't interact very well in any kind of
matter. And because a sensitive area is so

thin, it would basically permeate through
it and most of the times not interact and

doesn't make a signal. OK, what's really
important, since we don't want to measure

light, we have to shield light away. We
need to block all of the light, that means

easiest way to do it is to put it in a
metal case. There is electromagnetically

shielded and completely protected from
light as well. Electromagnetic radiation

or radiowaves can also influence these
detectors because they are super

sensitive. So this sould be a complete
Faraday cage, complete metal structure

around it. There's a lot of hints and tips
how to achieve that on the wiki on the on

the GitHub of this project. OK, let's
think about one of those PIN diodes,

normally there is one part in the
silicon which is n-doped

negatively doped, and the other part
usually, which is positively dropped. And

then you arrive at a simple so called p-n-
junction, which is a regular

semiconducting diode. Now, pin diodes add
another layer of so-called intrinsic

layer, here shown with the i. And that
actually is the main advantage. Why this

kind of detector works quite well and have
a relatively large sensitive Sigma's. So

if you think about, let's say, a photon
from an x ray or gamma-decay or an

electron hitting the sensor. So by the
way, this is a cross-section view from the

side, but that doesn't really matter. But
let's say they come here from the top into

the... into the diode and we're looking
at the side then we have actually

ionization because this is ionizing
radiation, so we get free charges in the

form of electron-hole pairs. So electrons,
which here the blue ball and the red

circle would be the holes. And depending
on the radiation kind, how this ionization

takes place is quite different, but the
result is if you get a signal, it means

there was ionization. Now, if just this
would happen, we could not measure

anything. Those charges would quickly
recombine and on the outside of the diode,

it would be a little signal. But what we
can do is we can apply actually a voltage

from the outside. So here we just put a
battery. So we have a positive voltage

here, a couple of volts. And then what
happens is that the electrons would be

attracted by the positive voltage and the
holes will travel to the negative

potential. And we end up with a little net
current or a small bunch of charges that

can be measured across the diode as a
tiny, tiny current. The sensitive volume

is actually proportional to the voltage,
so the more voltage we put, the more the

bigger is our volume and the more we can
actually measure with certain limits, of

course, because the structure of the pin
diode has a maximum thickness just

according how it is manufactured. And
these properties can be estimated with

C-V-measurements. So here you see an
example of a couple of diodes, a few of

the same type. The two that I've
mentioned, they're different versions. One

has a transparent plastic case. One has a
black plastic case. Doesn't really matter.

You see, basically in all the cases, more
or less the same curve. And as you

increase the voltage, the capacitance goes
down. So it's great and basically shows us

those silicon chips are very similar, if
not exactly the same chip. Those

differences are easily explained by
manufacturing variances. And then because

this actually, if you think about it, it
looks a bit like a parallel plate

capacitor and actually you can treat it as
one. And if you know the capacitance and

the size, the area, you can actually
calculate the distance of these two plates

or basically width or the thickness of the
diode. And then we arrive at about 50

micrometer, if you put something like 8 or
10 volts. OK, now we have a tiny charge

current, now we need to amplify it, so we
have a couple of diodes, I'm explaining

now the electron detector, because it's
easier. We have four diodes at the input

and this is the symbol for an operational
amplifier. There are two of those in the

circuit. The first stage is really the
special one. So if you have a particle

striking the diode, we get a little charge
current hitting the amplifier. And then we

have here this important feedback
circuit. So the output is fed back into

the input, which in this case makes a
negative amplification. And the

amplification is defined actually by this
capacitance here. The resistor has a

secondary role with the small capacitance.
It is what makes the output voltage here

large. The smaller the capacitance, the
larger the output and it's inverted. Then

in the next amplifier step, we just
increase the voltage again to a level that

is useful for using it later. But all of
the signal quality that has been

achieved in the first stage will stay like
that. So signal to noise is defined by the

first stage. The second one is just to
better adapt it to the input of the

measurement device that's connected. So
here, this is a classic inverting

amplifier with just these two resistors
define the amplification factor. It's very

simple. It's just a factor of hundred in
this case. And so if you think again about

the charge pulse and this, the circuit
here is sensitive, starting from about

1000 liberated charges in those diodes as
a result from ionization. We get something

like 320 micro Volt at this first output,
and this is a spike that quickly

decreases. Basically these capacitors are
charged and quickly discharged with this

resistor and this is what we see here. And
then that is amplified again by a factor

of 100. And then we arrive at something
like at least 32 mV, which is conveniently

a voltage that is compatible with most
microphone or headset inputs of computers

or mobile phones, so that the regular
headset here has these four connectors and

the last ring actually connects the
microphone. The other is ground and reft.

Left, right for the earbuds. OK, how do we
record those pulses? This is an example of

1000 pulses overlayed and measured on an
oscilloscope here. So it's a bit more

accurate. You see the deposits a bit
better, kind of like the persistence mode

of an oscilloscope. And the size of the
pulse is proportional to energy that was

absorbed. And the circuit is made in such
a way that the width of the pulse is big

enough such that regular sampling
frequency of a sound card can actually

catch it and measure it. Yeah, this is
Potassium Salt. This is cut here. This is

called a low salt in the UK. There is also
a german variance, you can also just buy

it in the pharmacy or in certain organic
food stores as a replacement salt.

On the right side is an example from this
small Columbite Stone, which has traces of

uranium on it. And this is measured with
the alpha spectrometer. And you see those

pulses are quite a bit bigger here. We
have 50 microseconds and here we have more

like one milliseconds of pulse width. Now
there's a software on a browser. This is

something I wrote using the Web Audio API
and it works on most browsers, best is

Chrome, on iOs, of course, you have to use
Safari and that records once you plug the

detector, it records from the input at 48
or 44.1kHz the pulses. Here's an example

with the alpha spectrometer circuit, you
get these nice large pulses. In case of

the electron detector the pulse is much
shorter and you see it, you see the noise

much more amplified. This red line is kind
of the minimum level that the pulse needs

to trigger. This would be better. And
that's like the trigger level of an

oscilloscope. And you can set that with
those buttons in the browser. You need to

find a good value. Of course, if you
change your input volume settings, for

example, this will change. So you have to
remember which, with which settings it

works well. And it is pulsed, for example,
is even oscillating here. So for electron

detector, it's basically nice to count
particles. For the alpha detector it's

really the case where the size of the
pulse can be nicely evaluated and we can

actually do energy measurements. And these
energy measurements can be also called

spectrometry. So if you look closer at
these many pulses that have been recorded

and we find that there is really like much
more intensity, which means many more same

pulses were detected, we can relate it to
radium and radon. If we use a reference

alpha source and I have done this, I have
measured the whole circuit with the reference

sources and provide the calibration on
GitHub and you can reuse the GitHub

calibration if you use exactly the same
sound settings that I have used for

recording. And for example, these two very
weak lines here from two very distinctive

polonium isotopes from the uranium decay
chain. The top part here which is really

dark, corresponds basically in the
histogram view to this side on the left,

which is electrons. Most of these
electrons will actually enter the chip and

leave it without being completely
absorbed by it, but alpha particles

interact so strongly that they are
completely absorbed within the 50

micrometers of sensitive volume of these
diodes and OK here is a bit difficult to

see peaks. But the far end of the high
energy spectrum, you see two really clear

peaks and those can only stem from
polonium, actually. I mean, we know it's

uranium and that can only be polonium,
which is that isotope that produces the

most energetic alpha particles and
which is natural. And I said, if you use

the same setting like me, you can use it.
So the best is if you use actually the

same soundcard because they're if you put
it to hundred percent input sensitivity,

you will have exactly the same result,
like in my calibration case. And this

soundcard is pretty cheap, but also pretty
good. It costs just two dollars and has a

pretty range and resolves quite well, 16
bits and think, oh, you could do that with

Arduino as well, is actually a bit hard to
do. A really well defined 16 bit

measurement, even at 48 kHz. It's not so
easy and this keeps it cheap and kind of

straightforward. And you can have just
some Python scripts on the computer to

read it out. And this is as a reminder, in
order to measure alpha particles, we have

to remove the glass here on top of the
diode. So I'm doing it just cutting into

the metal frame and then the glass breaks
away easily. Is not a problem, there's

more on that on the wiki. Now we
can kind of compare alpha and gamma

spectrometry. Here's an example. This is
the uranium glazed ceramics. The red part

is uranium oxide that was used to create
this nice red color in the 50s, 60s, 70s.

And in the spectrum we have two very
distinctive peaks and nothing in the high

energy regime. Only this low energy range
has a signal. And this corresponds

actually to uranium 238 and 234 because
they use actually purified uranium. So all

of the high energy progeny or daughters of
uranium, they're not present here because

it was purified uranium. And this
measurement doesn't even need vacuum, I

put it just like this in a regular box. Of
course, if you would have vacuum, you

would improve this peaks by a lot. So this
widening here to the left, basically, that

this peak is almost below the other one.
That is due to the natural air at regular

air pressure, which already interacts a
lot with the particles and absorbs a lot

of energy before the particles hit the
sensor. So in terms of pros and cons, I

would say the small sensor is quite
interesting here in an alpha spectrometry

because it's enough to have a small
sensor. So it's cheap and you can measure

very precisely on specific spots. And on
the other hand, of course, the conditions

of the object influence the measurement a
lot. So, for example, if there's some

additional paint on top, the alpha
particles might not make it through. But

in most of these kind of samples, alpha
radiation actually makes it through the

top, a transparent paint layer. In terms
of gamma spectrometry, you would usually

have these huge and really expensive
sensors. And then the advantage, of

course, is that you can measure,
regardless of your object, you don't

really need to prepare the object a lot.
You might want some lead shielding around

it. That's again, expensive, but you can
do it. You can improve the measurement

like that. And it's basically costly
because the sensor is quite expensive.

Vice versa in the set setup for 15 to 30
euro. You have everything you need and

here you're looking at several hundred to
several thousand euros. OK, now measuring

I have to be a bit quicker now, I noticed.
So I talked about the potassium

salt. There's also fertilizer based on
potassium baking powder. Uranium glass is

quite nice. You can find that easily on
flea markets. Often also old radium

watches. Here's another example of a
uranium glaze, the kitchen tile in this

case, this was actually in the kitchen. So
the chances are that you at home find

actually some of those things in the
cupboards of your parents or your

grandparents. It is an example of
thoriated glass, which has this

distinctive brownish color, which actually
is from the radiation. And a nice little

experiment that I can really recommend you
to look up is radioactive balloon

experiment. Here, you charge the balloon
electrostaticly and then it would catch

polonium from the air. And it's really
great. You basically get a radioactive

balloon after it was just left for 15
minutes in a normal regular room. OK, now

the last kind of context of all of
this to end this presentation, I want to

quickly remind how important these silicon
detectors are for places like CERN. It's a

cross-section of the ATLAS detector. And
here you have basically the area where the

collisions happen in the ATLAS detector.
So this is just a fraction of a meter. And

you have today 50 to 100 head on collisions
of two protons happening every 25

nanoseconds. Not right now, but soon
again, machines will be started again next

year. And you also can, by the way, build
a similar project which has a slightly

different name. It's called Build Your Own
Particle Detector. This is Atlas and made

out of LEGO. And on this website, you
find a nice plan, how to build or ideas,

how to build it from LEGO to better
visualize the size and interact more with

particle physics. In case of the CMS
detector. This is the second biggest

detector at CERN. Here you see nicely that
in the middle, at the core of the

collision, you have many, many pixel and
microstrip detectors which are made of

silicon. And these are actually 16 m² of
silicon pixel detectors and 200m² of

microstrip detectors also made of silicon.
So without basically that silicon

technology modern detectors wouldn't work
because this fine segmentation is really

required to distinguish all of these newly
created particles as a result of the

collision. So to summarize the website is
on GitHub, there is really this big wiki,

which you should have a look at, and
there's a gallery of pictures from users.

There's some simulation software that I
used as well. I didn't develop it, but I

wrote how to use it because the spectra
can sometimes be difficult to interpret.

And there's a new discussion forum that I
would really appreciate if some of you had

some discussions there on GitHub. And most
of the things I saw today are actually

written in detail in a scientific article,
which is open access, of course. And I

want to highlight two related citizen
science projects on the one hand, as the

safecast, which is about a large, nice,
sensitive Geiger-Müller based detector

that has the GPS and people upload their
measurements there. This is quite nice.

And also opengeiger is another website,
mostly German content, but also some of it

is English, that also uses diode
detectors, showed many nice places. He

calls it Geiger caching, places around the
world where you can measure something,

some old mines, things like this. And if
you want updates, I would propose to

follow me on Twitter. I'm right now
writing up two other articles with more

ideas for measurements and some of the
things you have seen today. Thanks a lot.

Herald: Well, thanks a lot, Oliver. I hope
everyone can hear me now again. Yes,

thanks for mentioning the citizen science
project as well. It's really cool I think.

We do have a few minutes for the Q&A and
also a lot of questions coming up in our

instance at the IRC. So the first question
was, can you talk a bit more about the SNR

of the system? Did you pick particular
resistor values and or Opamps to optimize

for noise? Was it a problem?
Oliver: Yeah, so noise is the big

issue here. Basically, the amplifier is
one I found that this around four, four

euros, trying to find the slide. Yeah, you
have to look it up on GitHub to the

amplifier type, but this is the most
important one. And then actually the

resistors, here, the resistance in the
first stage, sorry, the capacitors is the

second important thing. They should be
really small since I'm limited here with

hand soldarable capacitors. Basically I
choose the one that were just still

available, let's say, and this is
basically what is available is basically a

10 pF capacitor. If you put two of them,
one after another, you half the

capacitance, so you get five. And this, by
the way, is also then the capacitor. So I

kind of tried to keep the same
resistor values as much as possible, and

here at the output, for example, this is
to adjust the output signal for a

microphone input in the alpha
spectrometer, I changed the values quite a

bit to make a large pulse. But, yeah,
it's basically playing with the time

constants of this network and this
network.

Herald: All right, I hope that answers for
the person. Yeah, but people can get a

contact to you right after the show maybe
as well. So there's another question. Have

you considered using an I²S Codec with a
Raspberry Pi? radiation H80 should be

almost no set up and completely
repeatable. So last ones are for comment.

Oliver: I don't know that component, but,
yeah, as I said, using a sound card, it's

actually quite straightforward. But of
course there's many ways to get fancy.

And this is really this should actually
attract teachers and high school students

as well, this project. So this is one of
the main reasons why certain technologies

have been chosen, rather simple than,
let's say, fancy.

Herald: Yeah, so it should work with a lot
of people, I guess, and one another

question was how consistent are the sound
cards? Did you find the same calibration

worked the same with several of them?
Oliver: So if you want to use my

calibration, you should really buy this
two dollar card from eBay, CM108. I

haven't seen a big difference from card to
card in this one. But of course, like from

one computer to the mobile phone, it's a
huge difference in input, sensitivity and

noise. And it's very difficult to reuse
the calibration in this case. But you

still can count particles and the electron
detector is anyway, um, mostly it actually

just makes sense for counting because the
electrons are not completely absorbed. So

you get an energy information, but it's
not the complete energy of the electron.

So yeah, you could use it for x rays, but
then you need an x ray machine. So yeah.

Herald: Who doesn't need an x ray machine,
right? laugs So maybe one question I

have, because I'm not very familiar with
the tech stuff, but what actually can be

done with it right in the field. So you
mentioned some working with teachers with

these detectors? What have you done with
that in the wild so to say?

Oliver: So what's quite nice is you can
characterize stones with it, for example.

So since you can connect it to a
smartphone this is completely mobile and

it goes quite well in combination with a
Geiger counter in this case. So with a

Geiger counter, you just look around,
where are some hot spots and then you can

go closer with the alpha spectrometer and
actually be sure that there is some traces

of thorium or uranium on the stone, for
example. Or in this type of ceramic, these

old ceramics, you can go to the flea
market and just look for these very bright

red ceramics and measure them on the spot
and then decide which one to buy.

Herald: OK, so that's what I'm going to do
with it. Thanks for for highlighting a bit

the practical side, I think it's really
cool to educate people about scientific

things as well. Another question from the
IRC. Didn't you have problems with common

mode rejection by connecting the device
through the sound card? If yes have you

tried to do a AD conversion digitization
on the bord itself already? Transfer

transfer wire SP dif?
Oliver: Yeah, so, of course, I mean, this

is the thing to do, if you want to make a
like a super stable, rock solid

measurement device, but it is really
expensive. I mean, we are looking here at

15 euros and yeah, that's the reason to
have this separate soundcard just to

enable with some very low resources to do
this. But I'm looking for these pulses. So

this common mode rejection is a problem.
And also this is kind of Überschwinger -

I'm missing the English term. This is kind
of oscillations here. If you design a

specific analog to digital conversion, of
course, you would take all of that into

account and it wouldn't happen. But here
this happens because the circuit can never

be exactly optimal for certain soundcard
input. It will always be some mismatch of

impedances and.
Herald: All right, so maybe these special

technical issues and details, this could
be something you could discuss with Oliver

on Twitter of maybe Oliver or want to join
the IRC room for your talk as well. People

were very engaged during your talk. So is
this always a good sign. In that sense I'd

say thank you for being part of this first
remote chaos experience. Thanks again for

for your talk and for taking the time and
yeah, best for you and enjoy the rest of

the conference of the Congress and a warm
round of virtual applause and big thank

you to you, Oliver.
Oliver: Thanks, I will join the chat room

right now.

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