EEVblog - 2017-08-19
Dave tears down the Keithley 617 Electrometer, capable of measuring sub-femtoamp (attoamps!) resolution. Low Level Measurement Handbook: http://www.tek.com/sites/tek.com/files/media/document/resources/LowLevelHandbook_7Ed.pdf Forum: http://www.eevblog.com/forum/blog/eevblog-1017-enter-the-world-of-atto-amps/ Video on the relay matrix: https://www.youtube.com/watch?v=-mavHYV-H6o EEVblog Main Web Site: http://www.eevblog.com The 2nd EEVblog Channel: http://www.youtube.com/EEVblog2 Support the EEVblog through Patreon! http://www.patreon.com/eevblog Donate With Bitcoin & Other Crypto Currencies! https://www.eevblog.com/crypto-currency/ EEVblog Amazon Store (Dave gets a cut): http://astore.amazon.com/eevblogstore-20 T-Shirts: http://teespring.com/stores/eevblog 💗 Likecoin – Coins for Likes: https://likecoin.pro/@eevblog/dil9/hcq3
I made a common-mode joke
but it was filtered
Whaa ha ha ha haaaa hhaaaaa
you seem to be dealing with the rejection well
Nude virgins with grey beards. LOL. I knew a couple old ham radio guys who fit that description.
How do you even make a 250 gig resistor? Teflon windings?
Yeah I wonder how too. Must be some sort of doped semiconductor.
Simple it's just an insulator that is not really good at it's job.
The same way they manufacture ordinary through hole 1% precision and better resistors.
They can easily change the resistance value of the resistance material they use like fex at ordinary carbon film resistor but to get precision they need to do things a little different and they cant get fex 250 GOhm at a small length.
They cover the outside of a ceramic rod (could also be a tube) with the highest resistance material they have and then tune the resistance by doing a long spiral cut (easily seen on the rsistor) in the material so the signal has a long way to go through the resistance material and thus make a resistor of a very high value. The longer the spiral cut the higher the value and they can fine tune a resistor this way like they do with ordinary 1%, and better through hole resistors that are built in the exact say same way as the 250 GOhm one but much smaller due to smaller value.
So there are not anything special with them but they cost since they are not made in huge amount since they are only used in special circumstances, and that goes especially for the 250 GOhm one which will not be easy to get a hold on.
@EEVblog do you mean the gray bearded virgins or the resistors?
Use a "Bic Biro"
"Keep your used solder wick" Dangerous business giving engineers more excuse to hoard more 'useful' bits and pieces
Unfortunately true, but when doing soldering/ desoldering things more or less regularly you might end up finding some left over pieces in your junk bin in your Lab? ;-)
I'll keep my reel of solder wick until its used up then recycle it. Heat it up enough to melt it and the copper/tin/lead will separate.
@Simon Tay If you don't snip it off ever few millimeters, so you end with pieces of a few centimeters, These tinned braided pieces are useful as flat high current battery interconnects, when soldering Li-ion cells.
Btw. Do you know where the names "femto" and "atto" come from? They are derived from the danish numbers femten (eng. fifteen) and atten (eng. eighteen).
Didn't know that!
Off topic (sorry): Australia and Denmark have a very close royal relation (and an Opera one). The coming danish Queen Mary was born on Tasmania...
Hi Dave, I love your channel very much. Though I'm an electronics engineer like you, I find a lot of inspiration watching your work.
So was it Ørsted that got that idea for the naming? He did make a scientific dictionary, to invent Danish scientific words.
https://en.wikipedia.org/wiki/Femto-
Femto- (symbol f) is a unit prefix in the metric system denoting a factor of 10−15. It was added in 1964 to the SI.[1] It is derived from the Danish word femten, meaning "fifteen".
carefull dave, if you hold it sideways the electrons will fall out and skew your 62,5 electron count
Wonder if the Earth's magnetic field could mess with it in any way?
Julie Brandon Not that I'm aware of rotational field effects in such things, but would be interesting to test.
But after you have the field fixed (or in a know frequency) it will afect all the circuit ... when you mesure it in a differential way they will nuled each other.... because the metal can make the field homogeneous (at least more) over all the circuit
EEVblog could you do a video on hi power switching, like trigatrons, krytrons, thyrotrons, etc...
@Fauser Neves eh, magnetic north isn't the same as true north, that's probably gonna mean that the magnetic field strength/direction changes slightly over the course of the day in an annoying fashion. Wonder if this is affected by cosmic rays?
Really like to see a video explaining guards vs ground.
Thats not the correct explanation, is it?
What do you think it is?
Short answer: Insulators aren't perfect and current leaks through them if a potential difference exists across them. Because normal coax cable maintains the shield at a potential of 0 volts and your signal is not 0 volts, small amounts of current leak through the cable's dielectric from the signal-carrying conductor to the shield. Triaxial cable has a guard shield between the conductor and the grounded shield. This guard is maintained at the same potential as the signal. Because there is no potential difference between the conductor and the guard, no current can flow between them, thus helping to eliminate leakage currents. Guards can also be applied to PCB design since currents leak between PCB traces.
I guess that's not really super-short but it's more nuanced than saying that guards don't have current going through them. They totally do because they'll be leaking some current to ground, etc. but the important thing is that your signal is not the part that leaks.
OK, well, if you want to give it all away like that, sure, I guess you're right. I prefer my pithy one-liners.
Guards carry no current.
sorry Dave, had to flag this as extremely pornographic ;)
Attoamps = a bee sneezing on a wire causing a few electrons to move.
literally true: 1atto Ampere equals to about 6 electrons per second! And deformation in the lattice of the conductor can easily move thousands of electrons. Even if the material is not piezoelectric.
@Adam Rak Not that insane. You can buy fairly cheap low noise op-amps that operate in that range. I once made an amp for a seismometer, that took input from a pendulum connected to a piezo speaker. Literally I could stomp with one foot on the 3'rd floor and have it register in the basement.
Oh my word, I found a Keithley 617 in a skip a year ago! It's in working order and I had no idea it was capable of that kind of range! It will now be treated with even greater respect, I'm glad I rescued it. Cheers Dave.
At 14:59 the 250gΩ resistor is a lowly 5% tolerance unit. 5% of 250gΩ is 12.5gΩ or 12,500,000,000Ω. Anyone even seen a 1gΩ resistor? Sheesh!
If you rub your butt cheeks on the carpet this could measure the static charge.... NICE!
Nude virgins with grey beards? XD
Doesn't really make sense. You can't be a virgin and have a grey beard.
Sure you can Simon! Just wait till you're old enough to have a grey beard! :P
I kid... I kid... That'd be me... ;_;
wizard status
"Nude Virgins with Grey Beards" ~ Dave Jones 2017
18:10 little fail with the text & image there :D
Must be making mistakes purposely to push his youtube agenda!/s
I had a laboratory professor (The director of laboratory education for the whole school of engineering) who pronounced "femtoamps" as "fememtoamps" (rhymed with pimento)
I never figured out whether this was just his dry sense of humor, or if it was just his quirky way of saying that word, sort of like people that say "masononary" bit instead of "masonry."
This reminded me of the Bob Pease "what's all this femtoamp stuff" article and lab segment on National's video.
Dave, time to upgrade uCurrent puppy!
"i'll just plug some sharp probes up it's clacker" love engineer speak :D. Also diggin the 70s coffee and cream panel design there
2:23 should be 1 Ampere = 1 Coulomb/second
Shit. I thought an atto amp is some interesting amplifier. That's how alien it is.
2:29 There's that word again. "Heavy." Why are things so heavy in the present? Is there a problem with the Earth's gravitational pull?
Samgab yes!
Please do a video on guard grounding and star grounding too!
4:50 Oh no! You're missing a finger!
You didn't even mentioned Mexico :-|
15:24 I appreciate the quality work of those nude virgins with grey beards...
But goodness, I hope to never see one!
About 20 years ago I was looking a good use for atto-. I'm .0192 atto-light years tall.
You are 182 micrometers tall?
I came up with the attoparsec. If I calculated it correctly, it's about the largest diameter cylinder I can comfortably grasp in one hand - roughly three and a half inches. :)
1:57 Fempto ? => Femto
Yesterday I could spell engineer and now I are one.
EEVblog : it's speld injunear. Sum tymes hard to tell you is one.
Nude virgins with grey beards...
How do i get this image out of my mind?
Even more crazy that this STATE OF THE ART gear is .... HOW DID THEY CALIBRATE THIS THINGS ?. I mean, there most be something even more presice out there .... mind blowing. Now, you can even breath on this can. The stand offs remind me to RF stuff.
Giant eagles
Ultimately, it comes down to rubbing rocks together in a specific pattern. See 'automatic generation of gauges'.
They've got a guy with a realllly steady hand to calibrate the tuning pots
Watch Dave's video "how to calibrate a calibrator".
During the 70's NASA hand ground mirrors to within 1/6 of the yellow wavelength. Or so H&CF leads me to believe.
11:10 was pretty classic. Joke about the industry followed by an old electronics induced Dave moan.
On the PCB notes at 21:00 it's mentioning using Freon to clean the board.
What would you use these days, seeing as CFC's are banned?
Would probably be fine using other common refrigerants (e.g. R134a/1,1,1,2-tetrafluoroethane). You would have to be really careful about additives and contaminants however
A great cleaning solvent is Ensolve. It's a bromopropane product with incredibly low surface tension and low boiling point. Its optimized for vapor phase cleaning systems and pretty benign on plastics.
I have to admit I initially thought this video was about audio amplifiers from a brand named Atto.
Nevertheless, it was worth the click, very interesting and informative.
Hey dave, love these videos with high tech (and sometimes old) test gear. first the good old Fluke and now this beauty
Dave, aren't you wary you might knock a precision instrument like this one out of spec by poking around in it?
Nah it's been engineered to be fairly forgiving.
I'm relieved, whew!
Compared to the whack this thing got in shipping (see how the mains transformer was off-kilter), Dave's poking is gentle.
20:30 - "Do not TAUNT this Keithley 617!"
I like how often you add new videos these days!
Thanks, I'm trying, but still think I'm slow, lots of other stuff happening.
At 9:17 it looks like there's a gaping hole where solder should be on the most right lower pin of the chip above the Motorola.
That's the Dave we know and love, ie tech and laughs.
I etch my PCBs and all I think is about how thin and weak those copper foil traces are, and how the old point-to-point can handles so much more.
Definitely I have to measure Adam Ants regularly :D
I know femto amps, but when I read Atto Amps I thought it was some amplifier brand haha
christ dave there is precision and then there is precision. this was amazing
Dear lord he touched it....
"Watch Keithley 617 get down and dirty!
going down on those amps! sucking every electron ;)"
Nice video Dave! I noticed misspelling on femto and Coulomb in the video... I can see why your YouTube proposition is so important! The amount of work and time that goes into production with a highly technical topic is huge! I'm not picking, just mentioning. We all got the point and learned something all while being entertained, well done!
Ha, I just use the 10MΩ resistance on my multimeters voltage input in the 200mV range to measure low currents.
Sadly it's only reasonable in the 14kV to 50kV range of applications.
Very nice vid, thank you Dave! :)
Haha I've never heard of Atto mentioned.
240/120
:D
12:05 LOL love it.
Fantastic. Great educational video. Thank you!
Bob Cunningham - 2017-08-19
I've got war stories from my electronics lab technician job (before and during my time at uni), including one about building a 13-decade logarithmic ammeter that started down at 10 fA (calibrated), that added 3 lower decades to an existing 10-decade system. The PhDs did the circuit physics, the EEs did the circuit design, but I had to build and test the prototype, calibrate it, push it through DFM (make it repeatable and stable), then write the build, test and tech manuals for it.
Counting electrons is totally nuts: They never wind up going where you want them to. I had to enclose my lab bench within a Faraday cage. I had to remove the anti-static mats, clean everything with Freon, alcohol and/or acetone to remove residue traces. Special cables, special solder, special flux; nothing was standard. I had to take many of my measurements remotely.
The signal source was a unique and ultra-sensitive "current chamber" radiation detector driven by high voltage (~12kV) that was located 100m away, meaning it was connected using ultra-low-leakage coax. A nightmare to develop and test in the lab. The cable capacitance alone was horrible to deal with.
Precision log amps are strange circuits. We put a matched Darlington pair in the feedback loop of a Burr-Brown instrumentation amplifier. Simple, right? Not when we had to surround it with bias and thermal corrections to maintain sensitivity and log-linearity. Which added circuit load, which meant I had to start my testing and calibration a full decade lower, at 1 fA. Which meant detecting down to 100 aA to ensure we could reliably measure 1 fA so we could repeatably calibrate from 10 fA. Ugh.
Once the prototype was working, I had to build 10 pre-production units for environmental and accelerated lifetime testing, to ensure the calibration held for the required time under all required conditions. Double-ugh.
My main technical contribution was to thermal stability: I replaced the heat sinks and thermal straps with a machined block of copper, to ensure the instrumentation amp and the Darlingtons were kept within a fraction of a degree of each other, so the thermal compensation circuits would always work as intended and the calibration would be stable. (We almost had to go to a temperature-stabilized oven, but that would have created a cascade of problems that could easily have made things worse overall.)
At the last minute they changed both the PCB conformal coating and the potting compound. Not something you want to do around calibrated low-leakage high-impedance circuits (despite the new compounds being better). To avoid complete retesting, I "handled" it by redesigning the heatsink to become a sealed box, keeping the new materials far away from my calibrated log amp.
While it was a ton of fun, it was this project that convinced me to switch my major from EE to CE (computer engineering), though I did keep an emphasis on sensor/signal processing.
Actually, being an embedded/real-time instrumentation software engineer who is also a fully qualified lab tech has proven to be an ideal career choice for me. I can prove to the EEs where and how they screwed up, but I don't have to fix it myself! Bwa-ha-ha-ha!
Richard Commins - 2018-05-19
I worked at femtoamps and attoamp levels for my 36 year career. I have a video on YouTube that will show you how wrong you are on your cleanliness levels, interference problems, cost and size. Just type in "Femtoamp Measurement on Your Desktop" on Youtube. Everyone leaves off the bandwidth of the measurement because they don't understand the difference between accuracy, resolution and the speed of the measurement. Try measuring 1 femtoamps at a Noise Bandwidth of 22 Hz and see what you get! LOL Put 200 uV into a 200 Gig ohm resistor to produce 1 femtoamps of current and you will see a peak to peak Johnson Noise of around 5 femtoamps alone from the resistor. I challenge the EEVBlog to produce a 1 femtoamps current and measure it to a 100 attoamps accuracy at a NBW=22Hz. Don't forget to put that current into a 2 foot long cable on your desktop and see what kind of noise your cable makes. LOL My special cable uses $3 connectors and the low noise cable runs about $1 a foot.
Adamant Adam - 2018-09-15
I think I found the true definition of evil.
Paul - 2018-12-26
Sounds like a good job to me, much better than I have had.
IvoK - 2019-04-28
more philosophical question would be "was this thing ever used, and used to make what?" ie any of the 10 pcs made.
MrGoatflakes - 2019-06-16
Imagine doing it with all the bullshit about no freon, no lead, no halides (lol wtf?!) utter lunacy that rules the roost nowadays D: