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EEVblog => EEVblog Specific => Topic started by: EEVblog on March 23, 2021, 01:24:56 am

Title: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: EEVblog on March 23, 2021, 01:24:56 am
Teardown of the new Keysight EDU34450A 5.5 digit Bench Multimeter

https://www.youtube.com/watch?v=SR-3l6yrAXM (https://www.youtube.com/watch?v=SR-3l6yrAXM)
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: YetAnotherTechie on March 23, 2021, 01:54:53 am
why are the guard traces split?
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Blue on March 23, 2021, 02:15:07 am
why are the guard traces split?

Good question!

I'm not sure if I like this instrument.

PCB is not enig, just bare copper. Ref could be way better - 7ppm/C. Duhh.
Terminals are made from what? And terminals are obstructing my hand when I press buttons (rant of all instruments).
And for 25% more you can get a Keithley with way better specs, functions etc.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: tkamiya on March 23, 2021, 02:58:06 am
Maybe some of the traces are on inner-layers for protection from moisture or condensation?

The comb over comb looking thing....  is it for condensation detection?
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: gamalot on March 23, 2021, 05:04:27 am
JH brand electrolytic capacitors are produced by a famous Chinese capacitor manufacturer Jianghai.

Jianghai and Hitachi jointly invested and established a company to produce electrolytic capacitors.

http://117.83.178.187/file/upload/2020/03/26/CD263.pdf (http://117.83.178.187/file/upload/2020/03/26/CD263.pdf)
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: EEVblog on March 23, 2021, 06:04:21 am
why are the guard traces split?

Not sure. They go to dedicated pins.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: M.Zohaib Usman on March 23, 2021, 06:05:52 am
Maybe some of the traces are on inner-layers for protection from moisture or condensation?

The comb over comb looking thing....  is it for condensation detection?

Exactly! I'm pretty sure it is, he should've tried shorting it out after powering it on just to see what it does.  :-/O
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Cnoob on March 23, 2021, 09:33:27 am
From 6.36 on the video I noticed what looked like to be rust on the edges of the chassis .
Also Keysight put the model number on the screen just below the model number on the case. (20.00 on the video)
I will stick to my 34465A
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 23, 2021, 10:23:29 am
From 6.36 on the video I noticed what looked like to be rust on the edges of the chassis .

So they copied the Sigilent typical rust  :-DD

Some rust is fast to come up with water based detergents used to clean the metal work.

There is plenty of spacing with the input protection - more than to expect from a Chinese handheld DMM with CAT 4 specs. Interesting to have the spark gaps to PE and not so much between the terminals. After all there essentially 4 terminals (the current input is kind of connected to COM) - so the ohms sense inputs seem to have no such protection (at least not so visible, may still have a PCB sparc gap) - just the long chain of resistors.

The custom chip nearly looks like a special DMM chip like found in handheld DMMs.

With a price point not that much lower than the 34460, it is a bit disappointing in some respects. At least the trend chart would be really nice to make use of the large screen. Also the acquisition mode with a max. speed of 1 SPS is rather slow - it looks like the meter should be capable of more (at least some 30/25 SPS for 1 PLC). 

The Clicking from auto-ranging is a bit annoying, especially as it is quite fast. One can see a similar effect with other meters. AFAIR the HP3478 has a similar issue, though there it was not just mains hums, but the input bias slowly charging the input capacitance until the 10 M divider is engaged to discharge the cap. At least the clicking was slower.  It may be hard to avoid this effect all together - the hum related part should be relatively easy to detect.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: jusaca on March 23, 2021, 12:46:21 pm
This meter really looks way to crippled to justify that price point... Sure, they don't want to loose customers of the big toys to this cheaper alternative, but it just makes a pretty uninteresting product. If you can afford the little gap to the DMM6500 you definitly have a loooot more value for your money ;/

With that autoranging with open probes: If you go to lunch and accidentally leave the meter on the relays will be done before you get to dessert...
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Fungus on March 23, 2021, 01:05:05 pm
Seems awful/pointless on many levels.

* Couldn't even hear the continuity buzzer on the video. Had to turn the volume up to max.

* Weird button labels: eg. "DCI" and "ACI" for current? Who calls it that?  :-//

   Is it so that it matches Ohms law's V=IR  (and if so, why isn't the Ohms button labelled "R"?)

* Is it really necessary to put "\$\Omega\$ 2W" on the Ohms button instead of just "\$\Omega\$"?

   (Took me ten seconds to figure out it wasn't "Watts" - "2 Watts or 4 Watts?" WTF? )

(https://www.eevblog.com/forum/blog/eevblog-1382-keysight-edu34450a-5-5-digit-bench-multimeter-teardown/?action=dlattach;attach=1200728;image)


Would love to see it side by side with the more sensibly labelled $120 OWON (https://www.eevblog.com/forum/testgear/owon-xdm1041-the-unknown-multimeter/) in the other thread.
(https://www.eevblog.com/forum/blog/eevblog-1382-keysight-edu34450a-5-5-digit-bench-multimeter-teardown/?action=dlattach;attach=1200708;image) (https://www.eevblog.com/forum/testgear/owon-xdm1041-the-unknown-multimeter/)
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: madires on March 23, 2021, 01:10:10 pm
My crystal ball thinks that there will be a promotion soon: buy T&M for more than US$ 3.5k and get an EDU34450A for free. ;D
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Neilm on March 23, 2021, 01:26:36 pm
Could that "touch sensor" be something to measure the board conductivity? Not sure why this would be as it is only 300 V CAT II, unless it is a hold over from another product.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: ace1903 on March 23, 2021, 01:35:43 pm
I was looking for RMS converter chip but couldn't find any on the teardown pictures.
Then checked AC voltage measurement specification and I they seems bit low to me for this price range.
I know that all multimeters have wider tolerances on AC a ohmic measurement but this one seems to wide when spec-ed  as 5 1/2 digits.
Overall impression is that this toy has features of 150$  handheld multimeter and rest of money are just to make it bigger so no one will steal it from classroom.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Fungus on March 23, 2021, 01:55:17 pm
...rest of money are just to make it bigger so no one will steal it from classroom.

Also to impress the Dean when he visits the lab to see where all the money went.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: tszaboo on March 23, 2021, 02:39:42 pm
That coil-y part could be connected to some testpoints to verify board plating thickness.

The more I hear about this meter, the more disappointed I am about it. I was considering it as a work-from-home multimeter. But no, sorry. They made all the efforts to make it unusable as an engineering tool.

That voltage reference doesn't really give me the confidence. With 8ppm tempco? At least it is easy to replace it with something more accurate.
The temperature measurement is useless. It can measure temperature, but not a PT100. Or a thermocouple. Only one type of NTC.
The analog frontend seems a lot noisier than the 6.5 digit meters. Pun intended, switching relays is not acceptable.
No trend chart. 5000 point memory. But surely, if it only takes 1 measurement you can just log, to the USB, right? Right? No.
NPLC cannot be set. I guess it would confuse students? Maybe the teacher can explain what NPLC is so they learn something.

The specification is all over the place. Basic DCV, the most accurate range is the 1V one. Yes, not the 10V one. I guess it has to do with the 1.25V reference voltage.
Tempco is 0.0015 + 0.0008 (0.0008 is 8 ppm. the reference voltage is 8 ppm). For resistance the tempco is 0.0080 + 0.0005. So they use a more precise reference than the voltage reference.
I'd like to know what happened here. Did they run out of the flash memory of the microcontroller? Did a marketing guy bring a pen, and cross out every second feature from the 34465A?

Seriously, I think this DMM could be vastly improved by spending some extra effort on the AFE, and the firmware.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: joseph nicholas on March 23, 2021, 02:54:41 pm
Why tell you the model number on the case and again of the screen?  Kind of stupid.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 23, 2021, 02:58:49 pm
With that autoranging with open probes: If you go to lunch and accidentally leave the meter on the relays will be done before you get to dessert...

It is not hat bad: the switching is usually not that fast and at some 1 switching per second the meter could last a few months, though maybe not the full warranty period.
With a meter of this grade it is not needed to keep it running 24/7 and if one is in the room one would normally notice.

The Owon meter is in a different league. It lower resolution, has less PC interface and no 4 wire Ohms. It still has a very nice look and may for many uses be a alternative, though not a direct competition.
A more direct competition is the Sigilent SDM3055 (with a reasonable low bug firmware ).

At least the EDU edition is more competitive priced than the old 34450 version.

For the RMS ranges, the RMS converter could be inside the DMM chip  - at least I don't see much extra amplification part to use the µC internal ADC, which would be another low cost alternative.

No surprise that the 1 V range is the most accurate one - this range can go directly to the ADC. Chances are the ADC input range is some +- 1-2 V. The 10 V range would already go through the input divider. A high impedance 10 V range would take extra effort and this is not found in the 5.5 digit meter class.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: mikeselectricstuff on March 23, 2021, 04:00:33 pm
The exposed copper finger thing has 495 sq marked next to it, so it's probably a PCB capacitor used to calibrate out trace parasitics.
Humidty compensation ? Seems a stretch on something in this price range though
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 23, 2021, 04:27:26 pm
The exposed copper finger thing has 495 sq marked next to it, so it's probably a PCB capacitor used to calibrate out trace parasitics.
Humidty compensation ? Seems a stretch on something in this price range though
I would not expet compensation for humidity effects - not even found at 8 digits.
It may be a warning from too high humudity, which may be a safty hazzard - so maybe a carry over form an handheld CAT 4 design.
It could also be just a test structure to check board cleaning  - though from Daves picture they could do better, especially around the shunts (does not really matter there) and more important the high voltage divider.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: wizard69 on March 23, 2021, 08:17:33 pm
This meter really looks way to crippled to justify that price point...
Unfortunately I'm beginning to believe this.   I was really hoping for a good general purpose bench meter, not something half way between a high end hand held and a systems meter.   The reality is it is hard to find a good bench meter for the repair bench that doesn't cost an arm and a leg.

In this sense a bench meter has to have a large digit display as the number one feature.   The a reasonable range of features and performance.   Honeslty I would have preferred one less digit and a $400 price tag.
Quote
Sure, they don't want to loose customers of the big toys to this cheaper alternative, but it just makes a pretty uninteresting product. If you can afford the little gap to the DMM6500 you definitly have a loooot more value for your money ;/
More like a worth less product.   I mean honestly how many educational institutions will be buying this meter, especially on tight budgets.   HPAK had two choices here, make a ≤ $400 meter or fully enable this meter as a replacement for an existing model.   The high end can easily be managed by offering better specs and system meter features.   

What bothers me here is that HPAK apparently already has the software done for many of the missing features.   I hate to say this but they are effectively handing a very large market to the competition.
Quote
With that autoranging with open probes: If you go to lunch and accidentally leave the meter on the relays will be done before you get to dessert...
Obviously a partially tested meter.

Part of my disappointment comes from the reality that i really like a few of the concepts in the meter.   The large display with big digits is very desirable.   So far the actually panel lay out looks OK.   But then you have a continuity function that you can't hear.

The B&K 2831E is a better meter at less than $400 for the educational market.   Frankly it is a better meter for general use on most repair benches.   for people that need the resolution and accuracy you would be going upscale by a significant amount so this EDU meter wouldn't come into consideration anyways.

So agree 100% big disappointment.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: wizard69 on March 23, 2021, 09:00:25 pm
It is interesting that the similarly shaped OWON instrument is not listed on OWON's web site anymore.   Hopefully that doesn't mean this HPAK meter will go down the same route.   OWON has more conventionally shaped meters listed such as the XDM3041 which still are listed for far less than this so called EDU meter.   

By the way I'm not one to expect HPAK to compete price wise with a Chinese company that is new (somewhat) to the market.   I just don't see this meter as being remotely competitive with a lot of other established producers of test equipment.   I'm just not seeing the value here.

As I mentioned elsewhere I would really like to see HPAK take a different approach to upgrading their EDU hardware.   It is one thing to release early but when you have a habit of not adding to the initial release it just turns what is a poor value, into a extremely poor value over time.   It is reasonable to think that EDU's will buy in bulk so something like the OWON XDM3041 is likely to end up costing far less than $400, which would result in buying power of twice as many instruments as the HPAK offering.   Maybe that is what HPAK wants is the opportunity to offer bulk purchases at huge discounts.   You know the ability to convince a buyer that they knocked off $300 is pretty delicious.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: bdunham7 on March 23, 2021, 09:20:49 pm
My guess is that their business plan is to sell you the Keysight name with as little actual product as possible included in the deal.  Sort of like promotional t-shirts.  Anyone think the BOM on that thing exceeds $100?  How low could you go in large quantities?
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: ataradov on March 23, 2021, 10:00:08 pm
Another question is do student labs need 5.5 digit multimeter? We used venerable Mastech M830 in our physics labs, and it worked a charm. Typical labs don't need anything better. I'm not advocating for M830, of course, but if you are spending more than $100, you are probably just wasting money.

I can see there may be a need for improved performance in a research lab, but why bother with crippled EDU versions then? Just buy real equipment.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 23, 2021, 10:31:16 pm
The EDU meter is quite a bit (some $200) cheaper than the original 34450. In most aspects it is similar and the larger screen depends on the use. So it is not such a bad offer - still some extra for the KS logo and maybe some SW.  Compared to the Sigilent SDM3055 it is still quite a bit more expensive, but at least there is a chance to get at least the main SW bugs fixed.
Hoping to see a trend chart function may be a bit too much - but the hardware should be sufficient.

At least it looks like still an original Agilent design and not some rebranded Owon, Uni-T or similar.
For some reasone the OWON XDM3051 is also quite expensive - so there seem to some magic at the 5.5 digit level (or some premium paid by the market).


Most student labs don't need 5.5 digts. It is more that one may want  1 µV resolution. From the logic there should not be that much extra costs for the 5 th digit unless it comes with extra accuracy.
So a 5 digit meter makes sense, but the performance of the 34450 / XDM3051 or SDM3055 is still a bit disapointing.  They could as well habe 4 digits and a 10 mV range. I remember using an old nixi tube meter with 3.5 digits but a 2 mV range - would still be good enough in many cases.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: tszaboo on March 23, 2021, 11:03:16 pm
Another question is do student labs need 5.5 digit multimeter? We used venerable Mastech M830 in our physics labs, and it worked a charm. Typical labs don't need anything better. I'm not advocating for M830, of course, but if you are spending more than $100, you are probably just wasting money.

I can see there may be a need for improved performance in a research lab, but why bother with crippled EDU versions then? Just buy real equipment.
The labs we had were equipped with HO 54000 series scopes, 34401A, their test gear in general. Some of the labs were supported by companies they had newer gear. It does makes a difference, because after I got out, I could use the newer Agilent stuff, everything was where I thought it will be. It also set a standard in my mind, so when I saw a Tektronix TDS 2000 series, I saw how much hot trash it was.
If you have new high end gear in the lab, you can see how great it i s to have good tools.
If you have old high end gear in the lab, you can see how dependable and reliable these tools are.
If you have low end gear in the lab... That sends the wrong message.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: ataradov on March 23, 2021, 11:06:50 pm
That's all great from a company perspective. What do I care as a university if you like some vendor gear after you graduate?

Obviously of Keysight bundles that thing for free, it is fine. I just don't see the point of considering buying this outside of the bundled deal.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: maxwell3e10 on March 24, 2021, 02:41:19 am
Regarding 50/60 Hz rejection from the spec sheets of the meters:

EDU34450 NMR (normal mode rejection)  For 60 Hz (50 Hz) ± 0.1%
Slow mode 5½ digits, medium mode: 4½ digits, 60 dB
Fast mode: 4½ digits, 0 dB

34450 NMR (Normal mode rejection) For 60 Hz (50 Hz) ± 0.1%
Slow mode 5½ digits 90 dB
Medium mode 4½ digits 55 dB
Fast mode 4½ digits 0 dB

34465
Integration time    Normal mode rejection 1
≥ to 1 PLC                    60 dB 2
< 1 PLC                         0 db

So, according to spec sheet EDU34450 should have decent suppression of 50/60 Hz noise on medium or slow reading speed. Perhaps it wasn't properly set to 50 Hz?

But I agree that "fast" "medium" "slow" are annoying specifications, one should be more specific and, if used for education, teach engineering students about NPLC.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: wizard69 on March 24, 2021, 04:42:04 am
Another question is do student labs need 5.5 digit multimeter?
Personally I think the answer is no but a qualified no.  Students need understand when precision and resolution matters which is something not covered well in many schools.    In my opinion putting a 5.5 digit meter on every students bench is a mistake.   On the flip side students need exposure to an array of instruments. 
Quote
We used venerable Mastech M830 in our physics labs, and it worked a charm. Typical labs don't need anything better. I'm not advocating for M830, of course, but if you are spending more than $100, you are probably just wasting money.
Well we could discus the optimal price forever however a 4.5 digit  meter is more than enough to get students off to a good start. 
Quote
I can see there may be a need for improved performance in a research lab, but why bother with crippled EDU versions then? Just buy real equipment.

Exactly!   

What EDU needs is a low cost meter that exposes the students to as many potential measurement techniques as possible. 
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: floobydust on March 24, 2021, 04:58:47 am
I'd do a test and see if the mains (normal-mode) hum rejection is actually working. Should be a zero-cross detector on the board so the DMM can figure out line freq. as its predecessors did.
The DMM seems to spaz out way too much? I also don't find these Keysight bench multimeters (34461a, 65a) a good drive. The readings are all over the place, so much flicker it's like a slot machine in a casino to read them even with a dead quiet source like a battery. It's like it's picking up tons of strange noise that actually isn't external to the DMM.
Another test I would do is look at the common-mode noise the DMM has at the (-) input, with a scope or spectrum analyzer. You can a put a 10nF from (-) input to earth-ground to stop HF CM noise, assuming it doesn't already have that as a Y-cap from the floating A/D to PE.
I was disappointed to see Keysight copied ANENG by using Hongfa relays  :-/O and a 10k resistor across the coils seems weird.

A problem is the DMM looks expensive to manufacture - PCB with SMT on both sides, through-hole and flying leads, tons of manual assembly with the AC mains wiring, fuse etc. and a kilogram of shields over shields.
Instead of lowering cost by using cheaper components, a cost improvement project would first lessen manufacturing labour costs instead of relying on china for assembly.
Recycling the old enclosure and sheet metal saves development costs (NRE) but in the end it might add too much fat because it's not ideal - the power transformer +wiring are sources of hum but poorly shielded from everything and not away from the analogue board.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: 3roomlab on March 24, 2021, 07:20:44 am

I was disappointed to see Keysight copied ANENG by using Hongfa relays  :-/O and a 10k resistor across the coils seems weird.



the life expectancy (in words, no chart) from the HFD2 pdf (when plotted) is a straight line in log scale, very hard to believe it is a straight line in performace, i think it is impossible.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: gamalot on March 24, 2021, 08:29:07 am
I was disappointed to see Keysight copied ANENG by using Hongfa relays  :-/O and a 10k resistor across the coils seems weird.

Hongfa is not as bad as you think. They obtained UL certification in 1987 and acquired Hella's relay business at the end of 2019.

https://www.hella.com/hella-com/en/press/Company-12-11-2019-18428.html (https://www.hella.com/hella-com/en/press/Company-12-11-2019-18428.html)
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: tszaboo on March 24, 2021, 09:53:14 am
That's all great from a company perspective. What do I care as a university if you like some vendor gear after you graduate?

Obviously of Keysight bundles that thing for free, it is fine. I just don't see the point of considering buying this outside of the bundled deal.
They wanted to send students away with usable knowledge. It wasn't just theory. There is also a large pressure from automotive companies to teach communication protocol, like CAN and Flexray. It reduces the amount of training a graduate needs before being useful.
The class "Measurement technology 1" for example started by explaining how a scope works. And the underlying mathematics of error propagation and statistics.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: madires on March 24, 2021, 11:18:04 am
30 years ago the T&M lab of my university was equipped with typical stuff you'd have also found in commercial EE labs. And the communications lab had some fancy stuff like ISDN protocol analyzers. No special educational devices, all standard T&M. Not the latest and greatest, but devices which get the job done. And if you want to get students "ready for job" you should train them with standard T&M anyway. I don't see any point for overpriced educational T&M. A "my very first DMM" for a kid would be fine, but not for EE students. For hobbyists/makers a standard hand-held DMM is much better suited.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 24, 2021, 01:17:45 pm
For most part there is no special need for extra educational series. At least the 34450EDU is not especiall overpriced - it is some $200 less than the old version. There are a few cases (.g. RF gear) were extra robust instruments for educational purpose may be helpfull.

Other users may find those versions useful too - the difference is not that large and the form-factor may also fit a commercial bench.

There are companies to sell special instruments for schools. This is extra robust, extra safe (for use by the students) or with an extra large display, so that students can see it from a distance. These instruments may look overpriced (and sometimes underperforming) compared to normal T&M.

 
But I agree that "fast" "medium" "slow" are annoying specifications, one should be more specific and, if used for education, teach engineering students about NPLC.
A more accurate manual would definitely help, so one would know how the measurement actually operates. Most users would not mind, but it sometimes makes a difference.  It does not hurt to tell what the actual integration time and measurement speed is.

Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: rsjsouza on March 24, 2021, 01:59:30 pm
I personally don't dislike the form factor. This can potentially reduce the depth of benches which, at least in places located in prime realstate, is significant to pack more seats per m2. Also, it may well be a way for Keysight to test the waters to accept a new form factor - the circuitry of such devices does not demand the amount of bench space of its older brethren and therefore it may set a trend at least for a segment of the T&M market.

The internals are alright as well, although the reference is not the best and I hope the binding posts have some back support from the plastic enclosure - otherwise the PCB will be broken in no time.

The large display is very handy, but I didn't spot a "help" or "tutorial" button à lá Tektronix educational line. This could be handy for instructors and not a bad idea given the size of the display.

Being a 5-1/2 meter can help the instructor explain the various differences between accuracy, precision, resolution all in the same equipment. I see the value in this.

I obviously dislike the price for a single seat, although compounding it to an entire lab has significant savings when compared to the more professional tools from Keysight (Rigol/Siglent is another story, though). The lack of customizations and built-in trend/analysis tools, as well as the SW being a trial version, are bad ideas.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: jusaca on March 24, 2021, 02:46:10 pm
but I didn't spot a "help" or "tutorial" button à lá Tektronix educational line. This could be handy for instructors and not a bad idea given the size of the display.

This is actually one of the things Keysight is doing really well - you can press and hold any of the buttons and you will get a popup on the screen explaining everything around the corresponding mode / parameter / whatever the button is doing.
See for example the photo I attached: hold the button "HighRes" for something like 2s to get the popup. As far as I know, all their newer gear behaves like that.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: 3roomlab on March 24, 2021, 03:54:30 pm

Being a 5-1/2 meter can help the instructor explain the various differences between accuracy, precision, resolution all in the same equipment. I see the value in this.

I obviously dislike the price for a single seat, although compounding it to an entire lab has significant savings when compared to the more professional tools from Keysight (Rigol/Siglent is another story, though). The lack of customizations and built-in trend/analysis tools, as well as the SW being a trial version, are bad ideas.

i guess after adobe and altium
keysight also wants more subscription products
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: chickenHeadKnob on March 24, 2021, 07:03:37 pm

The internals are alright as well, although the reference is not the best and I hope the binding posts have some back support from the plastic enclosure - otherwise the PCB will be broken in no time.

The binding posts bothered me as well. I don't think the PCB's will break routinely. Instead if the board is allowed to flex I see the failure point happening at the solder fillet of the post, resulting in  dicky continuity and even more range-relay hunting Klackery.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 24, 2021, 07:58:30 pm
The mechanical load to the jacks / tubes could be a problem - actually split jack could have been the better choice as they are a bit more flexible. Still it would be mainly the solder joints that may turn bad - not sure how strong the lead free solder is. It least it would be relairable.


For the non populated BNC foot print where the ground lead is soldered, it looks like this was meant for some trigger input / ouput (e.g. measurement complete), but probably removed to save a few cents or not yet ready in time. The rear metalwork looks like different from the sope, as it does not habe the hole(s) for the fan.

I am a bit confused with the input bias current: with some 1.8 mV with 10 M input resistance this would be some 180 pA, so a relatively high input current.  I had expected better.

The large THT resistors for the AC input are a bit odd - I would more like expect a string of SMD ones. It could be just a take over from the older 34450 version.

From the specs sheet, the medium speed mode seems to be 1 PLC for DCV and DCI and 2 Wire Ohms.  Still odd to get less than 49 readings per second via LAN. The µC they have on ethe GND based side soes not look that slow.
Compared to the old 34450 they seem to have doen some cost cutting for the current ranges. Otherise it still looks very similar - so the numbering part is not that confusing.

Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Keysight DanielBogdanoff on March 24, 2021, 09:21:47 pm
My thoughts on this DMM. Disclaimer: I have the luxury of not needing to worry about price points or +- a couple few hundred bucks - my main personal experience is more about usability & capabilities.

I really like the big bright screen. I turned off auto-dimming almost immediately, but understand it could be nice for some folks since the screen is bigger and brighter than a typical DMM.

I've been able to pop it on my bench and use it without any issues and with a bit less of the usual 1st-time-user woes. I worked with Dave & our R&D on the relay thing and the beta firmware was much worse in that respect. For the NPLC stuff, the higher end DMMs have specific circuitry to detect and deal with that, this one doesn't for cost reasons. However, pulling it out of "fast" mode works wonders. As much as I like "fast" it's probably faster than I really need from my benchtop DMM, traditionally the super fast measurement frequency is more of a manufacturing line concern and I sort of prefer the longer averaging cycle (especially to get a higher NPLC).

Anyone think the BOM on that thing exceeds $100?

Handily, I've seen it.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: scopeman on March 24, 2021, 11:04:22 pm
When I first saw this I thought I must have overslept and it was April 1st already.
From my point of view it would make a lot more sense for Keysight to offer near cost discounts on the real gear for university and even senior high school labs than bringing out such strange crippled gear for the educational market.

After all when you graduate and get into industry would you really buy the EDU stuff? I think not. When I was in college we used the real stuff
HP/TEK/Fluke/GR etc. When I got out of school I knew what I wanted on my EE bench.

Sam
W3OHM
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 24, 2021, 11:39:28 pm
The fast mode for DCV / DCI is of limited use. Some 110 SPS can no longer suppress mains hum, but it cannot really resolve it either. So it is prone to hard to handle / detect errors from mains hum. The 190 SPS of the original 34450 is not that much faster, but about where a faster mode starts to make sense.

Fast readings make limited sense on the screen, but it can be useful for some data logging. So it would really make sense to write the data at some 50/60 SPS to memory or a USB drive. Just 1 SPS is rather slow for some experiments, though a good choice to get easy scaling.

Most younger users should not have too much trouble handling a few settings in the menu-system - so no real need to make it too simple / limited. It is still nice to have a dummy mode, but also nice to have control.

The EDU34450 is not that much different from the non EDU version: AFAIK less current ranges and lower grade shunts and slightl slower maximum speed. The performance range may be just the point were the chips for handheld DMMs reach there limit, and using seprate switches, amplifiers and ADC chip adds to the circuit and BOM. At least for the normal 5.5 digit meter it may be time for an upgrade.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Neganur on March 25, 2021, 12:28:57 am
Despite liking the display size and formfactor in general, I am having a hard time not spending the 300 EUR more to get the 34460A instead (thinking for home desk use). Or maybe even two of Dave's EEVblog handheld meters.

Isn't the DCA range a bit weird too?

I don't know what education market this aims at, not seeing many DMM at all in universities here in Finland. And if, then more the handheld type than the desktop ones simply because they are easier to lock away after use... Additionally, for proper scientific measurements you'd need the proper tools anyway. Maybe colleges are different? And does the education sector not get pretty substantial discounts anyway?
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: floobydust on March 25, 2021, 01:49:21 am
For student use, jack-detect to prevent a zillion blown fuses is obviously a good idea that was missed.
The auto-ranging algo sucks, have you not heard of successive-approximation? Why start at the bottom and work up, oh yeah to be the slowest in town. Hint: look at the middle middle middle.
Does diode-test display more than 3 sig digs on a 5-1/2 product? Why throw away resolution that was paid for, it's used for diode temperature use.
Can you make the font smaller and sillier on the (-) button please. And the beeper even more quiet. I like the big display, wish I could change font or colour.

edit: where's the Kensington lock
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: free_electron on March 25, 2021, 03:25:51 am
this thing is cool but disqualified for one and one reason only : you can't stack em or rack mount em. game over.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: EEVblog on March 25, 2021, 04:46:34 am
this thing is cool but disqualified for one and one reason only : you can't stack em or rack mount em. game over.

Their target market doesn't stack'em and rack'em though.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: CChin254 on March 25, 2021, 07:14:59 am
Design Wins:
[attachimg=1]
Predicted Block Diagram:
[attach=2]
IC Identification:
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 25, 2021, 07:45:54 am
KS offers some additional kit to stack them. It would likely still be limited (e.g. only 2 units and no power supply on top).

Isn't the DCA range a bit weird too?

I don't know what education market this aims at, not seeing many DMM at all in universities here in Finland. And if, then more the handheld type than the desktop ones simply because they are easier to lock away after use... Additionally, for proper scientific measurements you'd need the proper tools anyway. Maybe colleges are different? And does the education sector not get pretty substantial discounts anyway?

The fuse is not that sensitive - this is possible by using only 2 diodes (instead of a bridge) for the protection. On the downside this may limit the crest factor for AC amps and the usability for low currents. However the meter is far from providing fine current resolution, so the low current use is limited anyway.

The current ranges are a bit odd, but in parts due to cost savings: they use only 2 shunts and it looks like a seprate relative low noise amplifier (1/2 the AD8629). A low noise amplifier can use a single shunt and relay over a larger range - kind of makes absolute sense, as a low noise OP is cheap compared to extra shunts and relays.  I am a bit surprized to have the shunts with 0.1 and 1 Ohms. With the extra low noise amplifier I would have choosen more like 0.1 and 10 Ohms (or even 100 Ohms) to cover a larger range at not extra costs.  A 10 Ohms shunt could even be lower power.
A limited number of current ranges is common for cost savings and even some  digit meters like 34401 or Keithley2000 have this, though with more sensible values.

The large diodes make absolute sense, as they need to stand the current to worst case blow the fuse.

The physics / EE hands-on experiments at the university use quite a few DMMs. Here some bench meters could make sense. Because of costs there are still many handhelds. Bench top versions may be where higher performance is needed or where available (e.g. more like surplus or older units). Many cases could get away with a even lower grade version. Still the resolution is not so much driving the costs.

I would not consider the new meter exclusive for educational use.  Others can be happy with this meter too.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Fungus on March 25, 2021, 09:05:48 am
Isn't the DCA range a bit weird too?

You mean the "DCI" range?  :popcorn:
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Neganur on March 25, 2021, 09:39:37 am
woops, Freudian slip :P
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: tszaboo on March 25, 2021, 11:28:34 am
For the NPLC stuff, the higher end DMMs have specific circuitry to detect and deal with that, this one doesn't for cost reasons.
I specifically opened the 34401A schematic and looked up what circuitry this could be.
My guess would have been a optocoupler and maybe a TL431. But no, it is simpler.

This was the BOM of the NPLC detection:
One resistor, 42.2KOhm
One capacitor, 100nF
One zener diode, 6.2V. BZX84C6V2
You might need a lower voltage zener, but my estimated BOM cost of this is 2.1 cents. Surely it would've fit to the BOM. Just own up, that this is intentionally crippled.

Isn't the DCA range a bit weird too?
You mean the "DCI" range?  :popcorn:
They've been calling it DCI and ACI for the past 30 years. Just move on.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: temperance on March 25, 2021, 02:26:35 pm
-This "unconnected" comb like structure, might it be some test coupon which is specified in IPC2221B?
-TH component solder joints. What do you people think about the quality of the solder joints.


But maybe it's a good idea to learn students about relevant digits and basic accuracy. Till now I've met two engineers not able to correctly interpret the numbers shown on a DMM.

Case 1: this PFC circuit outputs 425.1V and the second one 426.2. Replaced many things and damaged the board while doing so...Charged the customer €800 for a new board in the end.
Case 2: this reference measures 5.12562V and the second one 5.142354 and the third one,..... But my circuit is also unstable because the last two digits are fluctuating.

I will need one of those when I'm 102 year old. I will be able to read its display without powerful binoculars at that age.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: 3roomlab on March 25, 2021, 04:58:29 pm
-This "unconnected" comb like structure, might it be some test coupon which is specified in IPC2221B?


i am thinking the production line has ongoing problems with surface resistivity of the PCB.
https://www.researchgate.net/figure/Photograph-of-the-test-SIR-PCB-pattern-used-for-testing_fig3_312295104 (https://www.researchgate.net/figure/Photograph-of-the-test-SIR-PCB-pattern-used-for-testing_fig3_312295104)

while browsing thru whats new, i stumbled on a yokogawa DL950. a freaking sync-ed scope system combining 160channels over fibre.  :-/O

back to my browsing around the web, i think i found what is likely the interesting piece of equipment (i see no reviews of it anywhere)

(4/U/L/R/G/S/P = 4wire/USB/LAN/RS232/GPIB/software/powerlinecycles)
prices are rounded up to $100 (*uses fast/medium/slow topology). XX = not std rack sized
+AAA = units with generally better overall specs than EDU34450 and $1k or less

no   model         Vrange/1yr spec         input-imp      features            price

0a    34401a          -10V 0.0035 +0.0005    @10G 4/R/G/P +LXI+labv 0.5k-data    (USD ~0.7k used)    +R    
0b    KS 34460A       -10V 0.0075 +0.0005      @10G         (USD ~1.3k)          +R
0c    KS 34461A       -10V 0.0035 +0.0005      @10G         (USD ~1.5k)          +R [replaces 34401a]
00    EDU34450A       -10V 0.025  +0.005       @10M 4/U/L/S/* 5k-data          (USD ~1k)          XX
01    KS 34450A       -10V 0.015  +0.005       @10M 4/U/G/S/* 50k-data       (USD ~1k)          +R
02   K2110          -10V 0.015  +0.002       @10M 4/U/S/P +labv 2k-data       (USD ~1.1k)         +R?   107mm
03    K2000          -10V 0.003  +0.0005    @10G 4/R/G/P 1k-data          (USD 0.6k used)       +R    
04    MP730028       -10V 0.015  +0.004       0.1G 4/U/L/R 1M-dat         (USD 0.7k)          +R? 110mm

05    8808A/SU       -20V 0.015  +0.005      @10M 4/U/R/S/P data?          (USD ~1k)          +R          
06    8845A          -10V 0.0035 +0.0005    @10G 4/R/L/P 10k-data          (USD ~1.3k)          +10vD       +R
07    DM3068          -20V 0.004  +0.0005    @10G 4/U/L/R/G/S/P +LXI 512k-data    (USD ~0.9k)       +R?   107mm    +AAA
08    DM3058          -20V 0.015  +0.04       @10M 4/U/L/R/G/S/* 2k-data       (USD ~0.7k)          +R? 107mm
09    SDM3065X       -20V 0.002  +0.0004    @10G 4/U/L/S/P 599k-data       (USD ~0.8k)          +R?   107mm    +AAA

10    SDM3055          -20V 0.015  +0.004       @10M 4/U/S/* 10k-data          (USD ~0.5k)          +R?   107mm   
11    BK 5493CG       -12V 0.0035 +0.0005    @10G?4/U/R/G/S/P +labv 10k-data   (USD ~1.2k)          +R
11    BK 5493C       -12V 0.0035 +0.0005    @10G?4/U/R/S/P +labv 10k-data   (USD ~0.9k)          +R          +AAA
12    BK 5492CG       -12V 0.01   +0.004       @10G 4/U/R/G/S/P 0.5k-data      (USD ~0.9k)          +10vD +R    +AAA
12    BK 5492C       -12V 0.01   +0.004       @10G 4/U/R/S/P 0.5k-data      (USD ~0.7k)          +10vD +R    +AAA
13    GDM9061       -10V 0.005  +0.0006    @10G 4/U/R/L/S/P 100k-data       (USD ~0.8k)          +R          +AAA
14    HMC8012       -40V 0.02   +0.002       @10M 4/U/L/S/* +LXI +labv 50k-data    (USD ~1.1k)       +R

15   R6552         -30V 0.015  +0.006?      @10M 4/R/G/* 1k-data         (USD ~0.3k used)       +R
16   ADCMT 7351      -20V 0.015  +0.002?      @10M 4/U/P/* ??-data         (USD ~0.8k)          +R
17   PXI4060         -25V 0.024  +0.001?      @1G  4/? ? ?               (??USD)             XX
18   Hioki 3239      -20V 0.016  +0.005?      @10M 4/R/G/* ??-data         (USD ~1.2k)          XX
19    DMM6500       -10V 0.001  +0.0004    @10G 4/U/L/S/P +LXI+labv 7M-dat   (USD 1.7k)             +10vD       +R
20   Hioki7276-02   -10V 0.0009 +0.00012   @10G 4/U/L/G/P 5k-data         (USD ~2.7k)          +R

21   3458A         -10V 0.0008 +0.00005   @10G                     (USD ~11.6k)
22   34470A         -10V 0.0016 +0.0002   @10G                     (USD ~3.5k)
23   K2002         -20V 0.0010 +0.00015   @10G                     (USD ~11.5k)
24   ADCMT 6581      -10V 0.0005 +0.0002      @10G
25   DMM7510         -10V 0.0014 +0.00012   @10G                     (USD ~6.4k)
26   8588A         -10V 0.0004 +0.00006   @10G


so guys .... which one will you buy? 
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: maxwell3e10 on March 25, 2021, 06:19:55 pm
Regarding NPLC detection, I am trying to figure out all possibilities:
1. Detect actual line frequency (every cycle or every few cycles) and use that as sampling interval
2. Trigger on power line but use a fixed sampling interval (automatically detect 50 or 60 Hz).
3. Trigger on power line and use a user-set line frequency (50 or 60 Hz) to determine sampling interval
4. Not trigger on power line and use a user-set line frequency to determine a sampling interval
5. Not trigger on power line and use a minimum sampling interval of 0.1 sec as common for 50 and 60 Hz.

I am not sure where different meters fall on this set of options.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: free_electron on March 25, 2021, 06:36:41 pm
i am thinking the production line has ongoing problems with surface resistivity of the PCB.

standard structure to test surface contamination. aka greasy fingers on precision circuit flagger.

Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: free_electron on March 25, 2021, 06:39:32 pm
this thing is cool but disqualified for one and one reason only : you can't stack em or rack mount em. game over.

Their target market doesn't stack'em and rack'em though.
i disagree. for education (or any other purpose) it is nicer to be able to stack a number of 1/2 rackwidth machines. a e34xx series power supply and a 34401 for example.
they need to kepe to 1/2 rackwidth machinery with all the same depth. it makes it easy on the bench to stack em. test equipment should be 19 inch or half width and should all be the same depth. so it can easily be combined into a 'stack'

I hate those non-standard width/depth devices.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: nctnico on March 25, 2021, 06:45:47 pm
this thing is cool but disqualified for one and one reason only : you can't stack em or rack mount em. game over.

Their target market doesn't stack'em and rack'em though.
i disagree. for education (or any other purpose) it is nicer to be able to stack a number of 1/2 rackwidth machines. a e34xx series power supply and a 34401 for example.
they need to kepe to 1/2 rackwidth machinery with all the same depth. it makes it easy on the bench to stack em. test equipment should be 19 inch or half width and should all be the same depth. so it can easily be combined into a 'stack'.

I hate those non-standard width/depth devices.
I agree to some extend. The fact is that you can fit a much larger (touchscreen) display in an 'oscilloscope' formfactor device. But it comes at the cost of stackability. Last year I bought a function generator with an oscilloscope form factor. It isn't stackable but the big screen makes it a whole lot easier to use.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: bdunham7 on March 25, 2021, 07:16:42 pm
Handily, I've seen it.

OK, I'll take your word for it.  I probably haven't properly considered the cost of the screen and such.  Still, the price/performance competition in entry-level test equipment is pretty brutal, although for some reason bench DMMs don't seem quite as competitive an area as oscilloscopes and handheld DMMs.  The big screen and form factor may carry the day for some people, but the performance and feature set is more in the 4.5 digit handheld category.  It may still be a good fit for some actual educational settings, but it's going to be tough to put many of those on working technicians' and engineers' benches.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: free_electron on March 25, 2021, 07:40:41 pm
I agree to some extend. The fact is that you can fit a much larger (touchscreen) display in an 'oscilloscope' formfactor device. But it comes at the cost of stackability. Last year I bought a function generator with an oscilloscope form factor. It isn't stackable but the big screen makes it a whole lot easier to use.
Why does a multimeter needs such a large (color) display. If it's a 51/2 digit machine all it needs is 6 7-zegment or starburst displays or a vfd. Let alone a touchscreen...
those things like chart plotting and recorder are gimmicks. if you really need recording you hook em up to a computer. That tiny display is useless. and nobody in his right mind will sit there zooming in and out on the chart. you need the data in excel or some other file anyway to do analysis.
color touch UI's for multimeters don't make sense. especially not when the machine still has 27 classic buttons next to the display as well... you either go all touchy ui without buttons or not at all.
another issue with touchy user interfaces is that machinery on the bench is typically stacked just at the border of reachability. you want to keep the bench open for the item under test. Touchy user interfaces lead to very tired arms very fast...
not very ergonomic.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: nctnico on March 25, 2021, 07:48:23 pm
I agree to some extend. The fact is that you can fit a much larger (touchscreen) display in an 'oscilloscope' formfactor device. But it comes at the cost of stackability. Last year I bought a function generator with an oscilloscope form factor. It isn't stackable but the big screen makes it a whole lot easier to use.
Why does a multimeter needs such a large (color) display. If it's a 51/2 digit machine all it needs is 6 7-zegment or starburst displays or a vfd. Let alone a touchscreen...
those things like chart plotting and recorder are gimmicks. if you really need recording you hook em up to a computer. That tiny display is useless. and nobody in his right mind will sit there zooming in and out on the chart. you need the data in excel or some other file anyway to do analysis.
That depends on what you need and what the device can do inside the box. If the device can show a chart and calculate min/max, average and standard deviation then you basically have 99% of the analysis requirements right there in the box. The graph gives you a visual view of the stability during the measurement and the numbers show you the statistical information. Again, it depends on what a device can do by itself. Personally I prefer to have all the analysis being done by the device itself since hooking it up to a computer usually isn't that straightforward and takes hours to mess with crappy software, drivers and incompatible versions. Been there, done that. Hard pass on anything that needs NI Visa.

Quote
color touch UI's for multimeters don't make sense. especially not when the machine still has 27 classic buttons next to the display as well... you either go all touchy ui without buttons or not at all.
IMHO that is mostly for people who still think they need to have buttons. On most touchscreen enabled test equipment I hardly use the buttons but some people insist on having buttons. MicSig for example offers versions of their tablet oscilloscopes which have buttons nowadays after starting out with button-less designs; it seems there is a large enough market for it.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 25, 2021, 08:29:56 pm
Regarding NPLC detection, I am trying to figure out all possibilities:
1. Detect actual line frequency (every cycle or every few cycles) and use that as sampling interval
2. Trigger on power line but use a fixed sampling interval (automatically detect 50 or 60 Hz).
3. Trigger on power line and use a user-set line frequency (50 or 60 Hz) to determine sampling interval
4. Not trigger on power line and use a user-set line frequency to determine a sampling interval
5. Not trigger on power line and use a minimum sampling interval of 0.1 sec as common for 50 and 60 Hz.

I am not sure where different meters fall on this set of options.

The first option is not really an option, if at all this would requite a PLL to generate a line synchrounous clock. It's quite some effort, but some old meters (Prema, Solatron, some Datron106x?) with long integration did that. It is less desirabel for shorter integration.

A user set option is found in few meters, especially those with battery option and still a higher speed than 10 reading per second. The multiples of 100 ms is very popular with battery powered meters as it is OK with a pure display orientation.

Auto detect between 50/60 Hz is quite common in mains supplied meter. It sometimes comes with the option to also trigger line synchronous. Depending on the meter internals it may not be needed for a SD ADC, as there are no separate signal and zero measurements as with more classical MS DMMs with higher resolution. As usual for a SD ADC chip or DMM chip set, there is no extra choice of a auto zero or non auto zero mode. In theory a SD ADC could have more options for the digital filter and could have simultaneous 50/60 Hz suppression even with less than 100 ms, at the cost of non equal weights.

The EDU34450 is kind of a odd meter, with a large screen and arguably nice UI, but the actual meter perfromance is more like at the lower end of the 5.5 digit meters. Not sure why they made the effort to save a few buck from the old 34450, which is allready not that great performance. A new 5.5 digit meter design, based on a modern of the shelf SD ADC chip should not be that complicated.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: maxwell3e10 on March 25, 2021, 09:01:22 pm
Regarding NPLC detection, I am trying to figure out all possibilities:
1. Detect actual line frequency (every cycle or every few cycles) and use that as sampling interval
2. Trigger on power line but use a fixed sampling interval (automatically detect 50 or 60 Hz).
3. Trigger on power line and use a user-set line frequency (50 or 60 Hz) to determine sampling interval
4. Not trigger on power line and use a user-set line frequency to determine a sampling interval
5. Not trigger on power line and use a minimum sampling interval of 0.1 sec as common for 50 and 60 Hz.

I am not sure where different meters fall on this set of options.

The first option is not really an option, if at all this would requite a PLL to generate a line synchrounous clock. It's quite some effort, but some old meters (Prema, Solatron, some Datron106x?) with long integration did that. It is less desirabel for shorter integration.

I think 3458 almost does it, it can measure and set an uneven line frequency, but I guess it doesn't do it continuously and automatically.

Quote
The EDU34450 is kind of a odd meter, with a large screen and arguably nice UI, but the actual meter perfromance is more like at the lower end of the 5.5 digit meters. Not sure why they made the effort to save a few buck from the old 34450, which is allready not that great performance. A new 5.5 digit meter design, based on a modern of the shelf SD ADC chip should not be that complicated.
I am not sure how EDU34450 can decide between 50 and 60 Hz if it doesn't have a trigger circuit and as far as I can tell from the manual doesn't have a menu option either. Perhaps it is a 50/60 Hz notch filter in the ADC.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: 3roomlab on March 25, 2021, 09:45:29 pm

I am not sure how EDU34450 can decide between 50 and 60 Hz if it doesn't have a trigger circuit and as far as I can tell from the manual doesn't have a menu option either. Perhaps it is a 50/60 Hz notch filter in the ADC.

i find the EDU34450 expression of acquisition to be really odd
the table on page 10, every function have a different SPS rate
i dont think it is trying to reference itself to PLC
can a fixed 50/60hz filter function? i cannnot see a common hz

compare this to BK5492, most things mentioned in the pdf is referenced to PLC in decades.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 25, 2021, 10:42:26 pm
There are no separate specs for 50 Hz and 60 Hz operation.  Even for the medium mode, there may be some additional averaging before display, as one can not really read the number at 50 updates per second - this would barely be the screen update rate. 10 SPS update rate is still relatively fast for the screen.
The old 34450 spec also show only one set of speeds - so maybe it is not using exactly 1 PLC for the medium mode either.

Chances are the slow mode is a multiple of 100 ms and thus natural simultaneous 50/60 Hz suppresion.

With a SD ADC adjacent readings may not be fully independent. So the reading rate may not directly reflect the integration time and the integration may not have a sharp start or end. Chances are the medium mode is a kind of compromise mode. There are kind of compromise filters, that can give some 60 dB NMRR for 50 and 60 Hz even with a reasonable fast rate.
https://www.analog.com/media/en/technical-documentation/application-notes/AN-611.pdf (https://www.analog.com/media/en/technical-documentation/application-notes/AN-611.pdf)
It takes a little more settling, but still faster than 100 ms.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: free_electron on March 26, 2021, 05:32:39 pm

IMHO that is mostly for people who still think they need to have buttons. On most touchscreen enabled test equipment I hardly use the buttons but some people insist on having buttons. MicSig for example offers versions of their tablet oscilloscopes which have buttons nowadays after starting out with button-less designs; it seems there is a large enough market for it.
mixsig has gotten it right. an oscilloscope leans itself nicely for touch . pinch to zoom etc. especially the newer version that has a couple of rotary knobs is really nice.

For a mulitmeter .. i don;t know. you can show some stats on the display if you want. but chart recording ? whenever i needed recording it was to plot behavior of a device over long time ( like battery charge / discharge ) , or pulsed behavior ( like a cellphone going from deep sleep to sleep to contacting the tower , to sending a message and going back to deep sleep. those are complex charts. not handy on a tiny screen. you want that data in a computer.
Same thing if you make a setup where you have an input multiplexer in front of your dmm. like when characterizing a D/A convertor.step ,measure, step , measure. you do that on mulitple devices, then run statistics between devices. none of that can be done on the machine itself. you need a data dump in excel or matlab.

ni-visa is the work of the devil. just install the base ieee-488 driver nd talk directly from excel. i have a small vba library that allows me to send scpi directly from excel and i made 'virtual instruments'

Code: [Select]

dim mydmm as new hp34401(17)   ' new 34401 at gpib 17
dim vcc as new TTI340(12,1) ' new thurlby tandar power supply gpib address 12 , channel 1
dim vee as new TTI340(12,2) ' new thurlby tandar power supply gpib address 12 , channel 2
mydmm.range = voltsdc20  ' set to fixed 20 volts range DC
mydmm.digits = 6 '
mydmm.nplc=10
vcc.voltage = 5
vcc.currlimit  =0.1
vee.voltage = 3.3
vee.currlimit = 0.1
tti340(12).alloutputson
tti340(12).attachexceptionhandler shutdown(event)

for x = 1 to 10
    vcc.voltage = 5v + (x/10)
    activecell.text = mydmm.read
    nextcol
    activecell.text = vcc.voltage.set
    nextcol
    activecell.text = vcc.voltage.read
    nextcol
    activecell.text = vcc.current.read
    newrow
next
tti340(12).alloutputsoff


sub shutdown(event)
     select case event
     case overcurrent
           tti340(12).alloutputsoff
           msgbox "overcurrent detected. system safed and stopped"
          end
     case else
         ' there ain't any others
     endcase
end sub

this would give me a table with dmm reading , set vcc , actual vcc (measured through the psu) , current draw on vcc
if i need ot do that on a device that has 4 output : instantiate a 34970 relay multiplexer and put another for-next loop that switches the relay.

Code: [Select]
mymux= new hp34970(15,1) ' gpib 15 , relay card 1
for y = 1 to 4
mymux.channel = y
  '  blabla
next y

i have virtualisations for all the instruments i use. if tomorrow i dont have a 34401 but a keithley 2002 all i do is change the instance. the virtual machines use the same syntax. so i don't need to alter my code.
mydmm = new keithley2002(COM1)  ' COM1 is constant larger than gpib address 32. if the driver gets an 'impossible' gpib address it subtracts 32 and opens COMx instead of GPIB
mydmm.serialinterface (9600,n,8,1)

the rest of the code is unchanged.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 26, 2021, 06:16:04 pm
The chart recording is sometimes nice when checking if the reading is stable. Something to differentiate between settling , drift and noise. It can also help to see if a recoded set of data is good (especially including the part of interest), before sending it to a USB stick - in case the DMM is not directly connected to a PC.  For a trend plot the slightly larger screen can be helpful.

Quite some experiments would measure more than 1 votlage. So it may be nice to have the option to use one of the ohms sense input as a 2nd optional input (a bit like the ratio function found in some higher end meters). From the HW side this should work for DC voltage in the 1 V and 100 mV range. It is a bit limited, but would be a relatively simple software only part.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: maxwell3e10 on March 26, 2021, 06:53:22 pm
What one would want in a modern benchtop DMM at a minimum is a trend display and ability to save data to USB stick (also faster recording than once per sec).  Something like Owon XDM3041 and Siglent SDM3045X do that. Otherwise, one might as well get an older used HP or Keithley meter for less than $200.   

But if one is equipping a student lab with 10 DMMs maybe Keysight makes sense if its going to be more stable than Owon/Siglent and one is spending someone else's money.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: floobydust on March 26, 2021, 06:57:27 pm
Any confirmation for what the USB port is good for?  F/W updates, stand-alone datalogging as a text file?
It can't display a histogram or bar chart or trend chart, unless you recall a log, I believe.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: SilverSolder on March 27, 2021, 02:50:55 am
why are the guard traces split?

It seems the guard emanates from the chip itself...  one on each side of the sensitive pin.  Maybe it just makes it easier to route the board?

Maybe the guard traces are driven?  Could be interesting to measure.

By not closing the guard traces - are there any advantages e.g. avoiding making loops that pick up magnetic fields etc. ?
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: WackyGerman on March 27, 2021, 06:18:58 pm
Could be that Siglent made this multimeter for Keysight . The Siglent rust is still included or is this an option which cost extra $  :-DD
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: tszaboo on March 28, 2021, 07:12:04 am

IMHO that is mostly for people who still think they need to have buttons. On most touchscreen enabled test equipment I hardly use the buttons but some people insist on having buttons. MicSig for example offers versions of their tablet oscilloscopes which have buttons nowadays after starting out with button-less designs; it seems there is a large enough market for it.
mixsig has gotten it right. an oscilloscope leans itself nicely for touch . pinch to zoom etc. especially the newer version that has a couple of rotary knobs is really nice.

For a mulitmeter .. i don;t know. you can show some stats on the display if you want. but chart recording ? whenever i needed recording it was to plot behavior of a device over long time ( like battery charge / discharge ) , or pulsed behavior ( like a cellphone going from deep sleep to sleep to contacting the tower , to sending a message and going back to deep sleep. those are complex charts. not handy on a tiny screen. you want that data in a computer.
Same thing if you make a setup where you have an input multiplexer in front of your dmm. like when characterizing a D/A convertor.step ,measure, step , measure. you do that on mulitple devices, then run statistics between devices. none of that can be done on the machine itself. you need a data dump in excel or matlab.
I have a standard, that calls for a temperature measurement, when the temperature settled, eg: It doesn't change more than 1K over 30 minutes. The output is the max value.
You can do average energy usage measurements for low power devices by just running it from the DMM. Onboard statistics gives you directly the end result. Only need to do a screen capture, and there is less possibilities for mistakes.
This is just two examples why it is useful.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: free_electron on March 29, 2021, 01:11:17 pm

IMHO that is mostly for people who still think they need to have buttons. On most touchscreen enabled test equipment I hardly use the buttons but some people insist on having buttons. MicSig for example offers versions of their tablet oscilloscopes which have buttons nowadays after starting out with button-less designs; it seems there is a large enough market for it.
mixsig has gotten it right. an oscilloscope leans itself nicely for touch . pinch to zoom etc. especially the newer version that has a couple of rotary knobs is really nice.

For a mulitmeter .. i don;t know. you can show some stats on the display if you want. but chart recording ? whenever i needed recording it was to plot behavior of a device over long time ( like battery charge / discharge ) , or pulsed behavior ( like a cellphone going from deep sleep to sleep to contacting the tower , to sending a message and going back to deep sleep. those are complex charts. not handy on a tiny screen. you want that data in a computer.
Same thing if you make a setup where you have an input multiplexer in front of your dmm. like when characterizing a D/A convertor. step ,measure, step , measure. you do that on mulitple devices, then run statistics between devices. none of that can be done on the machine itself. you need a data dump in excel or matlab.
I have a standard, that calls for a temperature measurement, when the temperature settled, eg: It doesn't change more than 1K over 30 minutes. The output is the max value.
You can do average energy usage measurements for low power devices by just running it from the DMM. Onboard statistics gives you directly the end result. Only need to do a screen capture, and there is less possibilities for mistakes.
This is just two examples why it is useful.
yes for such simple things.

 i guess i am more used to do device characterisation. Test devices if they follow spec. Sweep over different supply voltages, temperature ranges and do cross correlation with what the big testers see. or monitor a system (board test). those things invariably collect so much data that needs post processing anyway. Like do the inl/dnl of a DAC's. Do this over 25 devices on min , nominal and max VCC and from -25 to +125 degree in steps of 25 degree. such setups need to be driven as they can run for hours. board in the oven. 25 chips in sockets , input mulitiplexer , dmm , power supplies and oven all under software control. data spit into excel and immediately the spread plotted. those are typical things i used to do. not possible with the on board graphing stuff.

my criteria for a good multimeter are different
when it comes to measuring :
- stable and fast reading for volts and ampere and ohms
- predictable behavior (locking ranges. autoranging is the work of the devil in certain cases)
- high input impedance on volts
- low burden voltage on current
- remotability

-troubleshooting functions ( diode/zener/led test , capacitor meter , inductance meter , continuity , low ohms measurements (4wire) . touch-hold. min/max, temperature probe )
for these functions i don;t need top notch performance. i have a true lrc bridge if i need to characterize a cap or inductor.
troubleshooting functions are for handheld meters. a bench machine needs to excel in VOA , drift , stability and digits.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: nctnico on March 29, 2021, 04:21:30 pm
troubleshooting functions are for handheld meters. a bench machine needs to excel in VOA , drift , stability and digits.
That is nonsense IMHO. A handheld DMM sucks big time for bench use because it is always out of batteries, switches off just when you want to read it and the display is in the wrong orientation. Fortunately there are good bench DMMs for daily 'troubleshooting' use. Don't fall in the trap thinking that a bench DMM is a high precission instrument by definition. It isn't.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: tszaboo on March 29, 2021, 05:21:09 pm

IMHO that is mostly for people who still think they need to have buttons. On most touchscreen enabled test equipment I hardly use the buttons but some people insist on having buttons. MicSig for example offers versions of their tablet oscilloscopes which have buttons nowadays after starting out with button-less designs; it seems there is a large enough market for it.
mixsig has gotten it right. an oscilloscope leans itself nicely for touch . pinch to zoom etc. especially the newer version that has a couple of rotary knobs is really nice.

For a mulitmeter .. i don;t know. you can show some stats on the display if you want. but chart recording ? whenever i needed recording it was to plot behavior of a device over long time ( like battery charge / discharge ) , or pulsed behavior ( like a cellphone going from deep sleep to sleep to contacting the tower , to sending a message and going back to deep sleep. those are complex charts. not handy on a tiny screen. you want that data in a computer.
Same thing if you make a setup where you have an input multiplexer in front of your dmm. like when characterizing a D/A convertor. step ,measure, step , measure. you do that on mulitple devices, then run statistics between devices. none of that can be done on the machine itself. you need a data dump in excel or matlab.
I have a standard, that calls for a temperature measurement, when the temperature settled, eg: It doesn't change more than 1K over 30 minutes. The output is the max value.
You can do average energy usage measurements for low power devices by just running it from the DMM. Onboard statistics gives you directly the end result. Only need to do a screen capture, and there is less possibilities for mistakes.
This is just two examples why it is useful.
yes for such simple things.

 i guess i am more used to do device characterisation. Test devices if they follow spec. Sweep over different supply voltages, temperature ranges and do cross correlation with what the big testers see. or monitor a system (board test). those things invariably collect so much data that needs post processing anyway. Like do the inl/dnl of a DAC's. Do this over 25 devices on min , nominal and max VCC and from -25 to +125 degree in steps of 25 degree. such setups need to be driven as they can run for hours. board in the oven. 25 chips in sockets , input mulitiplexer , dmm , power supplies and oven all under software control. data spit into excel and immediately the spread plotted. those are typical things i used to do. not possible with the on board graphing stuff.

my criteria for a good multimeter are different
when it comes to measuring :
- stable and fast reading for volts and ampere and ohms
- predictable behavior (locking ranges. autoranging is the work of the devil in certain cases)
- high input impedance on volts
- low burden voltage on current
- remotability

-troubleshooting functions ( diode/zener/led test , capacitor meter , inductance meter , continuity , low ohms measurements (4wire) . touch-hold. min/max, temperature probe )
for these functions i don;t need top notch performance. i have a true lrc bridge if i need to characterize a cap or inductor.
troubleshooting functions are for handheld meters. a bench machine needs to excel in VOA , drift , stability and digits.
They clearly didn't made this with production testing in mind. There are no jacks on the back, trigger and complete is missing, and it is very slow for those sort of measurements.
In fact probably they probably limited the remote interface some unexplained way.

Like they wrote this for the EDUx:
Remote interface: USB, LAN standard
Programming language: SCPI-1994.0, IEEE-488.2

While the 3446x
LXI (rev 1.4)10/100Base-T Ethernet (Sockets, VXI-11 protocol, Web user interface) (Optional on 34460A)
USB USB 2.0 (USB-TMC 488 & MTP protocol)
Language SCPI-1999, IEEE-488.2, 34401A compatible

The old SCPI interface and the lack of specification for LAN doesn't increase my confidence.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Kleinstein on March 29, 2021, 06:33:34 pm
Given that the µC on the display side look quite powerful, it is really odd to have only a limited SCPI interface. Chances are this is taken over from the old version of the 34450 that also only supports the 1994 verion.
This meter is really not one build for performence. Many of the limitation may be from the DMM chip set - so it may be hard to change on some key paramters without a new design. Looks like the old 34450 is from around 2003 (at least thats the date of the EMC compilance tests - there may have been a predecessor), so it is a pretty old design. With most functions inside a special DMM chip more like a extended handheld than a cut down 6 digit meter.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: madires on March 29, 2021, 07:27:01 pm
Nothing odd, just business as usual:
We need an educational bench DMM for x bucks. Since it's 200 bucks less than our standard model it can't have the same features. Remove some! And don't make it too obvious! It should look like a new design. >:D
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: thm_w on March 29, 2021, 08:36:04 pm
Given that the µC on the display side look quite powerful, it is really odd to have only a limited SCPI interface. Chances are this is taken over from the old version of the 34450 that also only supports the 1994 verion.
This meter is really not one build for performence. Many of the limitation may be from the DMM chip set - so it may be hard to change on some key paramters without a new design. Looks like the old 34450 is from around 2003 (at least thats the date of the EMC compilance tests - there may have been a predecessor), so it is a pretty old design. With most functions inside a special DMM chip more like a extended handheld than a cut down 6 digit meter.

I'm guessing they won't reuse this processor in other high end models, it is powerful enough to do more as you say, but not near say the DMM6500:
- MPC5125YVN400 + 256MB DDR2
- STM32H750 + 32MB SDRAM (edu34450)

Nothing odd, just business as usual:
We need an educational bench DMM for x bucks. Since it's 200 bucks less than our standard model it can't have the same features. Remove some! And don't make it too obvious! It should look like a new design. >:D

yep, some companies are probably very strict about self competition.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: Fungus on March 30, 2021, 01:30:42 pm
Given that the µC on the display side look quite powerful, it is really odd to have only a limited SCPI interface.

Not "odd", deliberately limited by the marketing department.
Title: Re: EEVblog 1382 - Keysight EDU34450A 5.5 digit Bench Multimeter TEARDOWN
Post by: SilverSolder on March 30, 2021, 07:28:23 pm
Given that the µC on the display side look quite powerful, it is really odd to have only a limited SCPI interface.

Not "odd", deliberately limited by the marketing department.

A distant cousin of Planned Obsolescence?   >:D