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
Really like to see a video explaining guards vs ground.
Yep, will have to think up the best way to demonstrate that and test it first.
Totally agree, please do it! 😊😊
Thats not the correct explanation, is it?
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.
Guards carry no current.
"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.
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.
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.
carefull dave, if you hold it sideways the electrons will fall out and skew your 62,5 electron count
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?
@EEVblog Of course! Gravity is a thing which obviously will have some measurable effect on mechanical oscillations.
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!
Please do a video on guard grounding and star grounding too!
Interesting video Dave!!! Can you do a video on grounding and some basic pcb design guidelines? May be you can show effects of incorrect grounding and such in that video
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!
Hello, thank you for the great video again. What is the type of those shields? Are they made of some ferromagnetic materials like soft stell or mu metal? Or simply high conductive meterial like aluminium?
Hey dave, love these videos with high tech (and sometimes old) test gear. first the good old Fluke and now this beauty
+1 for guard and grounding for high precision measurements video!
That's the sort of videos I really enjoy whatching. In fact they could be like 2 hours in my opinion. :)
At this point I want to thank you Dave for your great videos, great explanations paired with humor. Your channel has brought me so much knowledge, keep going on!
-> I can't wait any longer for my training to start next month to get even more into this topics. :)
Thanks, and have fun with the training.
It's amazing how refined they got their equipment back in the day. In today's world it would not have an instruction on the case setup. The design is mind blowing. Loved seeing those long resistors at such high values. Those Mexican relays were something else. We don't see any off the board designs these days.
I love this stuff..thanks for the memories...I worked with the floating circuits starting in the late 80's. IIRC, my favorite Hi-z input op-amp was part# AD549. The old huge Analog Devices' famous thick--very thick--data books had all kinds of PCB design samples for Guard traces and the like.
OK, my question--a bit trivial....in the timespace between 18:04 and 18:14 I was wondering what the text actually read--it is hidden by a FET electroscope (?) front end graphic. I couldn't quite grab it.
I know femto amps, but when I read Atto Amps I thought it was some amplifier brand haha
Holy shit, my mass spectrometer typically has a 10E-15 amp signal o.o I didn't think it was possible to measure less than -16
Amateur :-P
lol, on an "off the shelf" helium mass spectrometer I don't think it is economical to measure less than -16 amps coming off the electron multiplier. The noise created from gasses desorbing from the test system surfaces are probably 2 or 3 decades higher and can cost as much as the mass spectrometer itself to eliminate.
It is fascinating though to think of a day where semiconductor manufacturing is so advanced that the processes need to be checked with a helium mass spec that is sensitive to 10E-14 atm. cc/sec. There are already there for QC checking MEMS devices so maybe another 10 years of development on the wafer side of things will get us there.
@CafeBikeGirl In practice I don't think it really is. Many measures would have to be taken to minimize noise from the environment to get any meaningful measurements that low. On a mass spectrometer spewing it's own noise all over the place, it is quite impressive in it's own right.
EEVblog: Thank you, thank you, thank you for this video. You've explained why my measurements were off. I used the non-nude virgins cable !! (or was it the nude-non-virgins? I forget.) It was as simple as that ! Once I got the right cables, everything measured as expected. Thank you again!
Nice video Dave. In the earlier days of SLR camera light measurement we developed log amps that had to be precise down to some 10 pA for lowest short circuit current of the photo diode. A good reminder of those days.
That occasional yawning in videos is EPIC.
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.
Nice reference to Jim Williams from Linear Technology! He was a master. I worked for Linear for 16 years and Analog Device has now purchased us. Great minds. Cheers!
"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
Good instrumentation withstands the tests of time.
Proper current-nutting yay :) Thanks Dave.
I like your enthusiasm. I'm trying to keep up to you. Whew! I'm nuts over your show. A shout out to the mrs. and Sagan. Peace.
Yippy another vid from the great man. I learn alot from you and have now got myself a lab where there is always something on the bench. Problem is I love it so much iv almost moved in haha.
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.
Thanks for cracking open the test equipment archive. Yeah Keithley.
Very nice vid, thank you Dave! :)
Fantastic. Great educational video. Thank you!
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.
@Hexane Very funny that your handle is hexane, as I have cleaned flux off with isohexane
Keithley kicks ass !! I have a bunch of the old 179A DMM's its still my fave bench meter because its small foot print and accuracy , you can null out the leads, and ease of calibration and maintenance . Did I say their cheap.
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.
wonderful episode. thanks a lot!!
15:38 part number TG-168-8524 (4, not A)
are there any further digits?
The caps in the PSU need to be replaced.
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.
Is very neat test gear, thank you for sharing.
I used this before, we used it to measure the resistance on the straps between the cells of UPSs.
I would love to see a video on making those super high resistance resistors. Those look really cool.
He probably can't upload it on Youtube. Assembled by nude virgins in full moon, you know...
A video on current guards and very low current measurements would really rock Dave ...its a bit late for me since I have been dealing with pA measurements in photo diodes for the last couple of years now ... but man getting your head around guards, high impedance measurements, and just pcb design and cleaning etc, below 1nA is really a big learning curve ... a fundamentals Friday on this stuff would have been an amazing help for me 3 years ago and hopefully others too !!!
11:10 was pretty classic. Joke about the industry followed by an old electronics induced Dave moan.
Cool, your videos always give me nightmares, where a piece of equipment such as that is put down on my bench, and the old professor from college is standing over me, saying "It is broke Mr. Ercisson , FIX IT!!" and there I Sit with absolutely no idea what it is even supposed to do, let alone knowing how to fix it. I usually wake up about the time I plug the unit in and try to turn it on. That said, I do love your videos, my shrink gave me some pills that stop nightmares so I can watch your videos again.
That electrometer is a god dam neat instrument.
Could it be used to used to measure the "forward leakage" or in other words, the forward current of a silicon diode biased with something around only 50mV?
Nice strip-down, I am adding one of these to my own lab today :)
Shit. I thought an atto amp is some interesting amplifier. That's how alien it is.
Dave, time to upgrade uCurrent puppy!
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.
With turtles... it's always turtles all the way down.
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".
Definitely I have to measure Adam Ants regularly :D
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!
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:
Ronnie Pirtle Jr - 2020-03-26
I got to work as a laborer back in 1991 at a power plant in Indiana. It amazed me some of the dangers that a person could run into. For instance, several holes in the floor throughout the building about 3 or 4 stories up, large enough for 2 men to fall through with nothen but a panted line around the hole to warn you. No guardrails! I looked down in the Hole with a concrete floor below and thought.. oh crap, don't want to step there! My labor job was, after the asbestos removers had removed the asbestos insulation from around the broiler, I was one of the grunts that would put the new thick wool insulation back in its place. There was also a gap, that runs around the boiler ledge, on each level that a person could fall down to the level below, we had to be careful! I am going to guess that Maybe it was around 18in wide/ half a meter? The coolest part that I remember was they were overhauling a turbine. This turbine was about the size of a UPS truck. This turbine had 4 armed guards with 12 gauges in hand, standing around it, while the engineers we're working frantically inside. I asked one of the guards if I could step inside for a second and check it out? I figured hell, the worst He can say is no!
But he didn't, he said "yeah go ahead". So I stepped inside & checked out the inside of this big turbine while the Engineers were working like mad men. Lol, they really were! I thought to myself..." how many people in the world get to stand in this exact location, in side this turbine? Because After they close this thing back up, it is sealed until the next overhaul!". they will pretty much have the same procedure again, but it's pretty safe to say that not just anyone gets to be inside one of those turbines!
Ora nge - 2020-04-24
@Mr. Morningstar I mean what you described is on like every "life hack" video ever
qwertyboguss - 2020-09-13
That's genuinely a cool story, bro.