Dave please do me a favor to turn on CC. I’m deaf need to read CC which helps me understand while you’re show and tell. Sometimes not all videos you setup are automatically turn on. There are millions of deaf and hearing impaired are learning from your greatest experts. Please support us that we love you, Dave. My picture hand signs means “I love You”. Cheers, AlpineJWH

Hi Dave, nice tear down, I fixed my HP34401A myself, works like a treat now. Great meter and can't wait to buy this new version...! Keep them coming!

whoa, this has got to be the most detailed teardown that i've ever seen!

Awesome! DaveCad got an upgrade! I was waiting for this!

I'll have to order two of those. Thanks! David Lee

you're on the right path bro.

engineering marvel, such a compact and well laid out design

About the re-cal, I'm sure that is probably a "better safe than sorry" thing. It _may_ mess with calibration. More importantly, if you need to work with certified calibration on everything then safe is probably better. So I would probably have written "voids calibration" if i were to write the manual; but it may be relevant.

So that constant current through the resistor magically flows into the opamp input? Or off into the ether? Or is gobbled up by the loch ness current monster? I won't play semantics.

I am currently studying electrical engineering at university. I have used Maxwell's equations very often, there is no way around them. One equation derived from the main equations (Ampere's law and is I = dQ/dt. Current the differential of charge over time. You have a current flowing onto one plate and that plate builds up a charge. That charge makes an electric field that attracts an opposite charge to the other plate. If charge flows to the other plate, you have current.

i have no idea what all these chips do but i still watch these videos

Yes, shooting this one was delayed, then it was a 2GB upload so took a long time.

It's more than just useful, it's an essential "simplification" (or more correctly "combination") for both practical electronics theory and practice. Welcome to the real world :->

Half an hour ago you asked me what I consider current flowing "through". I answered that an electron should be able to enter on one side and leave on the other. Only in an electrical current do you have charge that's actually moving. When you are talking displacement currents, you are talking about the change of displacement field over time through an area. Charge isn't moving (at least not between the cap plates).

c621 @32:14 next to the 10 bit ADC might be the cap you are looking for. Didn't look it up because it's hard to see the part

I saw this multimeter on Agilent'sKZfaq channel earlier today , and I wondered if you get to review it :) Great video!

Yeah, I need that HD!

In capacitor the electron from one plate do not go through the other plate, but there is current flow from one side to the other side :D That's what my prof told us.

What does the spark gap do? (labeled E101 on the board)

The smell of precision

if it's like any other soft off/on power supply, the standby circuit probably pulls ~5-10mA +/-2mA. it's heavily dependent on how conscious of the standby power draw the EE that designed the supply was.

If I'm not mistaken, it would be fairly atypical for the developers to leave the WinCE command shell running on the COM port, hence the lack of response. They may have never even used it; in the past, I've used COM for bootloader and startup messages, then a separate mechanism to access an embedded telnet server during development (which is subsequently disabled during production).

High voltage input clamping. MOVs have a specific rise time before they clamp when voltage exceeds their rating. An ionizing spark gap will clamp within microseconds (versus milliseconds) of the voltage reaching breakover. ESD can theoretically be clamped with a spark gap, but internal clamping diodes on the chip is better at that.

I was wondering if you were going to upgrade to wise screen Dave cad, I was even thinking about sending you some in a mailbag. 😎

Hi Dave, An excellent teardown video. I have two questions for you. (1) As you look into the multimeter just behind the front panel there is next to the large capacitor a small 3 legged component with the numbers 8DCNG inscribed on it. Next to it are the letters ERC. Can you please help me identify this component. (2) The second question I have is regarding a problem I am facing with my multimeter. When we power it on, majority of the times the self test fails and therefore prevents any further action. The LAN seems to be defective however the rear USB is functioning alright. The front USB has some issues because of which I am unable to update the frimware. That said, there are those rare times when the self test passes and the multimeter works beautifully (until powered off). This leaves me to believe that some timing related issue in the start up sequence is playing up. With Keysight's assistance over a video call, I tried to see if I could do a firmware update with little luck. I am given to understand that repairs of the multimeter by Kesight could involve one of two things - (a) replacement of the front panel board alone and (b) if that does not work replacing both boards. I am also given to understand that both these options could cost up to 40000 or 90000 Indian rupees depending on how many boards they have to replace. That seems steep when the price of a new multimeter is just over 100000 (and comes with a three year warranty). Is there any more advice you could provide me with to try and fix this problem?

I like more the way of the HP multimeters, which prevent the flow of air in and control the temperature. I think it is more stable

Because it does very advanced stuff. It makes sense to standardise on a high level OS. Windows CE is not the same as Windows though.

20:42 those are most likely bulk metal foil resistors from Vishay Precision. I've worked on a project using them before, pretty much a ideal resistor from a temp co and voltage coefficient point of view.

MR eev how do they multiplexing voltages in autorange DMM? Whatkinda switching what MUXs what resistors?

It would have been interesting if he would have run some test before and after to see if it did fall out of calibration after he removed that shield. But may be they mean if you take the shield off and never replace it?

Congrats, you just used the word current 3 times in trying to explain how current *doesn't* flow through a capacitor. Current flows on the plate, current flows off the plate, the current is equal on both sides - but it *doesn't* flow through! :->

I usually let it process into full HD before releasing, but it was already delayed enough, so left it public overnight and it went live before finishing. Still not monetised either, so I lose out on that.

No you are not correct. Current still "flows through" the capacitor, it's just a different kind of current. There is electric current, and displacement current at work in this circuit. They come under the same umbrella.

Like the Coilcraft inductors on the front panel...I would had expected to see them on the main board, considering the nature of this instrument...

The joys of working for yourself, you get to work any 12 hours a day you want!

It is in fact possible to combine the 10-bit and 8-bit ADCs to get higher resolution at full speed of these devices using the subranging ADC technique. A precision DAC and some custom logic does the magic. If there is a precision DAC somewhere near those two ADCs, then it's probably using subranging instead of dual-slope.

20:31: In the meantime this LM3S is obsolete. In the 2018 model Keysight used a TM4C129 controller instead.

1826-1249-5 is the full arbitrary in house part number for the LM399. That looks like a continuation of the 1820-xxxx series of part numbers that HP used in a lot of their stuff.

DaveCad Widecreen.. Brilliant! XD

Default u-boot allows serial uploads, although it's possible Agilent removed that. U-boot has its own command line interface with a lot of features. It would be interesting to abort the boot sequence and see what's available.

Just a noob question... why does the 3A terminal have a 11A fuse?

I love the new widescreen version of DaveCad

Text is already on the forum in 34461A thread!

Nice use of a pointed stick :) Far better (and safer) than a mini screwdriver ;)

Can you do on how to diagnose a pinball machine - driver board, power supply etc. 1977 and up solid state models???

How much did the "widescreen" version of DaveCAD set you back?

Would love to see a shootout with the Keithley DMM6500... my ancient HP 3478A is in need of retirement, still working great though.

Do you remember Ripterm for DOS. It had a graphical interface suitable for a low bitrate (2.4k-14.4k). I wonder if there is a standard like that for these modern times?

I hate coming here right after upload and considering watching it only in 480p or waiting to see fullHD :-D

That could allow to upload a custom kernel if the bootloader can take one over serial. Don't know anything about uboot though. The system might even have a mechanism that it only loads agilent signed kernels, too.

Is there any reason for the vias not to be tented here?

I'd say this is kind of a debatable area. Electronics enthusiasts/engineers often speak of current flowing through capacitors, but from a physicists point of view, it's a whole different story. Current is flowing onto one plate of the capacitor and an equal current is flowing off the other plate, so charges on both plates are always equal (the signs are obviously opposite). Because you have equal currents on both sides, people (including me) often say through, but that's not technically true.

you should've added some modem noises there Dave :D

12:00 For anyone watching this wondering how it works, its similar to the old 34401A's, you have to 'pull up' in the center, and push down on the arm on the side. No need for a screwdriver, but still a pita. Why the hell they thought this was a good was to clamp things together, who knows.

"Constant current flowing through that capacitor" ;). Sure thing Dave.

Question: how the discount was.

Kirchhoff's current law also applies. That alone is enough definition for anyone to use such the term. How can you say my use of the term is perfectly fine and commonly accepted, but then also say there is no EE definition?

Guess they had a massive mount of old SCSI connectors laying around.

[space] sent to RS232 at startup gets you into a pre-boot debug menu. Some dangerous looking things in there - see 34461a thread on forum.

"Our fuses go up to 11" :)

As far as I remember the one that comes with the PureView camera is a Symbian phone.

Your explaination is more useful, without a doubt. But all I'm saying is that if you wanted to nitpick, you would technically be right to say that current doesn't actually flow through the capacitor (that's what Andrew - the OP - was trying to say).

Dave! How could you do that to lovely ms. stockphoto!

I had a 25 hour working day recently. Fortunately, those don't come too often.

waths that under youre desk tht grey at 48:00

Displacement current (D) is an entirely different thing to electrical current (I). Don't mix the two. As I said, it is practical to explain the effect of charging as current flowing through the capacitor. Much easier than saying "the current that flows into one side and charges a plate, which causes the other plate to charge with an opposite charge, which causes an equal current on the other lead". That still doesn't mean current is actually flowing through it, but we can explain it that way.

Only the truly initiated will get it!

Because it needs LAN connectivity, USB, fonts, language support, firmware updateability etc. etc.and reinventing the wheel is expensive.

Equal charge building up at same rate on the other plate means that an equal opposite current is flowing onto the other plate. That explains why the current that flows into one plate is equal to the current flowing off the other plate. I had to split this comment in two, because I exceeded the 500 letter limit.

"It's getting into it, but it doesn't seem to be responding in any way.." The debug terminal was not loaded, so all you get is the output. Way back in the beginning you can interrupt the load and then you'll have a terminal. As for windows CE, scary. Amazed that Agilent built such a quality instrument with that crap as a foundation.

I know Dave loves quality, but I thought he once said bench multi-meters are a waste of space and money (He said in a old driving blog video). That hand-held meters are the way to go.

may be you should made twice test, before and after unpacking all of that thing

Dave ! Read about Ronald L. Swerlein and his "A 10ppm ACCURATE DIGITAL AC MEASUREMENT ALGORITHM" !!

Ah, makes sense.

Good for them for making use of a cheap chip for the front-end instead of going overboard and using a Cortex-M9...

Kind of disappointed to see the LM399 again in this new multimeter. My 30 year old 3478A also used this voltage reference, but it's just 5 1/2 digits.

I found that Realterm is the best free solution for hyper terminal. I use it to debug all my projects.

Srsly, just pause this video when he shows his face and there's always a funny expression he makes x3

At 19:19 your dyslexia decided to peek out didn't it! xD hahaha

why are there 2 11a fuses?, at the side of one it clearly says 3a.

Oops, I see Chris just explained that.

There is a parasitic resistance in parallel if u look at the replacement scheme für a real capacitor. So there is a current flowing. I found some SMD Capacitor with a parasitic parallel resistance as low as 10^8 Ohm. But yeah thats not what he was talking about i guess.

tensies! ;)

Yep, that could be it. I noticed a press any key to abort bootup message, maybe that's it?

48:50 it says press space to stop auto-boot that should give some access, but very very low level

Dave is right. Think about. Even an electronics trades certificate person, like me, knows that..

aus/nz (where im from and where dave is from) its thursday lol

One equation derived from the main equations (Ampere's law and Gauss's law) is I = dQ/dt. That's what I wanted to write, but I somehow messed it up when I was splitting the comment in two.

Yes, I know I messed it up with the displacement current and D. I should probably be going to bed soon.

How the voltage changes is correct, but the current does not go "through" the capacitor.

It is. Anyone who says otherwise is just playing silly buggers.

I think Andrew wanted to point out that the current isn't flowing THROUGH the capacitor. :)

Sell it quick, there might be a food of 34401's on ebay now.

The Indiana Jones model please!

Where would I be able to buy the T shirt?! Not the one you are actually wearing, but a new one!!!

2. It's normal if the backside is wave soldered.

Um.erxelente equipamento fica a pergunta seu display tem durabilidade baicha igual do multimeter u1253b esses display nao durao

Certainly! Just send Dave a (broken) pinball machine and I'm sure he'll do a teardown and try to fix the problem :)

Bah, I think by saying that it needs recalibration when you remove that EMI shield they just want you to check to see if it has come out of calibration. I honestly don't think they designed it to get out of whack just by removing a measly EMI shield.

Looks like they are using an old scuzzy connector for that front board lol