New eevblog multimeter?

[EEVblog]

This overload detection requires a fast sampling of the amplified signal, sort of peak-window detection, which is not implemented. Even in ACV it's not implemented, what makes me wonder. The fast internal A/D could serve this purpose.
Better DMMs feature a separate fast window comparator for that.
So you have to live with this weakness and may anticipate manual upranging, when you expect 'difficult', non-sinusoidal signals.

Yes. Kane have had a lot of problems with the HY3131 chipset, and have specifically noted that there are issues with using both internal (fast and slow) ADC's at the same time and/or switching between them.
They have even sent engineers to Hycon several times to try and resolve this sort of stuff, but it seems there are just inherent limitations in the chip. Particularly so when AC and DC share the same switch position, which is the issue with the volts autoranging. That's not unique to Kane either, other brand meters that share AC/DC volts knob position can also have issues with detection of autoranging with DC offsets on AC signals. It's why the new design meter uses separate AC and DC switch positions.

Hi Dave,
I again dug deeper into the schematic and the HY3131 datasheet. Latter already has a programmable, fast window comparator on board, both lower and upper limits are programmable everywhere inside the V_DD, V_SS range, which is intended for monitoring the output of OP1 .. can't understand why this could not implemented for ACI, at least.

Should also work for this ACV + DCV problem.
Yes, the ACV signal is routed over OP1 again to the external RMS converter.
Therefore this comparator should be able to detect any overload conditions also.

All I can tell you is that they have extensively looked into solving this, including I believe sending someone to Hycon to liase with them about it, and they could not come up with a solution for the AVC ranging issue.

[EEVblog]

Outside of what you may learn by looking into the 121, the end result's the same as it's clear, "I don't need design advice"
Well, there is just the pure fun of it....

If you don't have anything productive to add Joe please stay out of the thread.

[Kleinstein]

It looks like the auto-ranging is based on the RMS reading and done in software. So it should at least be possible to change the level when the next higher range is used. I would prefer it to step up to the next range a little earlier, possibly well before the actual maximum. So instead of some 5.4 mA the level may be already at 3 mA. This would reduce resolution / number of counts, but in the AC ranges one does not really need 50000 counts, as the accuracy is not that high anyway. The manual ranging would still give the full 5.5 mA range. I would expect the limits to be relatively easy to change, unless this goes all the way to ADC overload.

For voltage readings the high crest factor / clipping is not very likely, but for the current ranges a pulsed current waveform is quite common. The SCR and rectifier with a large filter cap case both look similar. So it would be nice to tolerate at least something like a crest factor of 5, even if this comes at a price (reduced range).

For AC readings the frequency is often known, so I would not give so much weight to the secondary frequency reading. The display of the crest factor like with the fluke 289 would be often more useful. The external RMS converter would not permit this, but the hy3131 internal digital RMS would allow this. If the hardware allows it would be nice to also have the option to use this RMS version. Here peak values and thus the crest factor would be available. In some respects the digital RMS should also have other advantages:  faster response, better stability, more accurate at the low end (e.g.< 1% of full-scale), detection of clipping and amplitude independent bandwidth, though lower overall BW.

[CDaniel]

No , it is not using the true-rms chip for autoranging , because in DC range for pulses has to take the same decisions .'
It is using the internal comparators or the fast ADC , the one showing the bargraph .
Now we can make all kind of suppositions , but an owner of Keysight U1282A  with HY3131 or other similar meter could tell very quickly if  the chip itself is "sluggish" or the 121GW implementation sux

[dcac]

Yes it is using the true-rms value from AD8436 for auto-ranging. And that’s why we’re having this problem. AD8436 have no idea if signal got clipped by hy3131 and hy3131 have no idea about the signal level before it samples the AD8436.

The ‘fast ADC’ is not used at all in 121gw with current FW. The bargraph gets its data from the main AD1 converter - the same that samples the AD8436.

But speaking of duty-cycle, currently in AC modes only the frequency is calculated but I think all data is there to also calculate the duty-cycle. If so no new configuration for the hy3131 is needed and the comparator can keep its function for frequency. And instead measured RMS voltage plus the measured duty-cycle is used to decide when/if to change range.

[CDaniel]

I can"t belive it is so bad ... How to use slow true-rms converter for autorange 

[PA0PBZ]

I set my HP8116A to generate 100Hz 10% duty-cycle  High level 500mV Low Level 0V
I connected a 50 precision termination (0.1%) and measured the voltage with a few of the meters that I have in the lab.

DG4062, terminated in 50 Ohm:

34461A: 150.9
BM235:  146.6
1241B:   150.6
87 III     150.0
Fluke 45 150.6
K. 197    150.6
3478A    150.5
PM2528  149.2

[MiroS]

Outside of what you may learn by looking into the 121, the end result's the same as it's clear, "I don't need design advice"
Well, there is just the pure fun of it....

If you don't have anything productive to add Joe please stay out of the thread.

Joe did much, much  more that anyone else here in order to make  121GW better 

[joeqsmith]

Outside of what you may learn by looking into the 121, the end result's the same as it's clear, "I don't need design advice"
Well, there is just the pure fun of it....

If you don't have anything productive to add Joe please stay out of the thread.

Joe did much, much  more that anyone else here in order to make  121GW better 

Thanks   

[tautech]

Outside of what you may learn by looking into the 121, the end result's the same as it's clear, "I don't need design advice"
Well, there is just the pure fun of it....

If you don't have anything productive to add Joe please stay out of the thread.

Joe did much, much  more that anyone else here in order to make  121GW better 

Thanks

Yes, a bit ironic that the famous TE reviewer that's picked holes in equipment for the last decade is not happy when the heat is turned up on his product.

[coromonadalix]

I would say its a learning curve, fw and hw issues, and maybe some checks who where never been tought  or situations we may never have/face while using a meter.

The newer model may benefit from this, and all 121gw related problems ...   the 121 was a first  in many things ...

And i'm sure Dave had put lots of efforts in this project.

And the forum brings lot of ideas, some do's and dont's, some cold, some hot   loll

[Dr. Frank]

Outside of what you may learn by looking into the 121, the end result's the same as it's clear, "I don't need design advice"
Well, there is just the pure fun of it....

If you don't have anything productive to add Joe please stay out of the thread.

Joe did much, much  more that anyone else here in order to make  121GW better  :clap:

Thanks

Sorry, no, I don't think so.
At first I dislike such malicious comments/video like you, Joe, made against Dave, or in general were made against anyone else in this forum in this mood.
2nd, making destructive tests which mostly exceed the usual test standards, is no constructive way to improve any DMM.
3rd, many other contributors have also identified many (more) failures and weaknesses in SW and HW of the 121GW.
4th, identification and complaining about these failures alone, especially often in a similar malicious way, for me does not give rise to improvements.
To my gut feeling, many different , other contributors have really made constructive proposals, which partly went into Engineering Changes and led to substantial improvements.

Dave, please keep on with your good work, and also your willingness to openly discuss such interesting design problems.

Frank

[floobydust]

Despite joeqsmith's harsh style and trollish tint, he is a constant reminder that it's not all unicorns and rainbows with the product. Instead of sweeping it under the carpet.
While nobody expects perfection or the crushing of Fluke's balls, I expect a spirit of improvement- which seems to be happening at a frustrating, minimal amount with the multimeter. The schematic is years old? Sorting out the input protection changes? No fun. On the other hand, Dave has given personal support 1000x that of any manufacturer. So it is a bit crazy making.

[EEVblog]

Yes, a bit ironic that the famous TE reviewer that's picked holes in equipment for the last decade is not happy when the heat is turned up on his product.

I could easily have instantly shut down any comment or discussion over the years, but have I ever done so? No, never.
But what I won't tolerate is people, regardless of the contributions they have made, continue to constantly make snide remarks and derail and pollute otherwise useful technical threads. There are several people that constantly do that, and they are continuing to do it again in this thread.

[tautech]

Yes, a bit ironic that the famous TE reviewer that's picked holes in equipment for the last decade is not happy when the heat is turned up on his product.

I could easily have instantly shut down any comment or discussion over the years, but have I ever done so? No, never.

You'd be a hypocrite if you did.

But what I won't tolerate is people, regardless of the contributions they have made, continue to constantly make snide remarks and derail and pollute otherwise useful technical threads. There are several people that constantly do that, and they are continuing to do it again in this thread.

Put yourself in their position Dave, they've invested good coin in one of your products and been disappointed in it for one reason or another of which AFAIK some potentially dangerous issues are still not addressed.

Snide remarks as you put or 'pointers' to flaws of many products and brands abound in this forum with advice of what to apply a 40' barge pole to are frequent yet subtle warnings about your products should be exempt ? 

This facet of the forum is allowed to prosper to the point where members signatures denigrate brands and you turn a blind eye to it like control of it could be conceived as moderation of free speech.

[CDaniel]

Well , nobody forced David to design and put his name on a multimeter to earn some extra money ... so he can expect all kinds of reactions if his multimeter is not as good or has obvious  flaws not resolved for years . Everything discussed here has a technical reason after all ...

[BU508A]

Criticism is okay as long as it is done in a constructive manner.
Some contributions here are probably based on facts but the undertone is sarcastic and in some cases hostile.

I don't like this.

I'd really appreciate it, if we could come to a good technical solution. Even the discussions around these issues
are very useful or do I have to remind you, that learning is based in a very lot cases on flaws, issues and mistakes?

So, please come down, have a cup of coffee or tea (or imagine sitting together at a nice place and have a good cold beer / drink)¹
take a deep breath and assume, that the person on the other side is really nice.

Thanks.

¹I'll bring some cakes.

[Wytnucls]

No meter is perfect, even from major brands like Fluke, Gossen and Keysight, as most of you have discovered.
Nobody was forced to buy that multimeter. If you think that Dave is not doing his utmost to iron out its perceived flaws, put yours up for sale and move on.
I don't see any used 121GW available on eBay or anywhere else at the moment, so have to assume that most owners are happy with their purchase.

[EEVblog]

Criticism is okay as long as it is done in a constructive manner.
Some contributions here are probably based on facts but the undertone is sarcastic and in some cases hostile.
I don't like this.

It's not just that, that's ok, but when they do it over and over and over again, sometimes for hundreds of posts, it has to stop.
People who are unhappy with their meter have been offered a full refund, but they don't take me up on the offer, instead it seems to be some kind of sport to them to continually pollute the forum threads about it. And it's just happening again with this one.

[EEVblog]

So what's the deal with this new meter?
As I said, it "just appeared", I had absolutely no input to it nor knowledge of it. If you want to know why they did it, it seems like they want to extend their 500 series line with a higher end meter. Predominately sold in China I believe, but could be in other markets.
http://www.kanetest.com.cn/category.php?id=36
http://www.kanetest.com.cn/goods.php?id=109

They decided to take the 121GW and put it in a bigger case, up the CAT rating, add true power measurement, motor measurement etc
Also, it's supposed to solve the DC offset issue by using separate AVC and DCV ranges.
The exiting line already had Bluetooth.
They kept stuff like the SD card logging, low burden, but dropped the 15V diode mode.
I had no idea they even had these existing designs.

[Wytnucls]

There is a UEi DM525 with bluetooth and power measurement already ($260.00).
Is it the same 6000 count meter in a different case?

[BU508A]

So what's the deal with this new meter?
As I said, it "just appeared", I had absolutely no input to it nor knowledge of it. If you want to know why they did it, it seems like they want to extend their 500 series line with a higher end meter. Predominately sold in China I believe, but could be in other markets.
http://www.kanetest.com.cn/category.php?id=36
http://www.kanetest.com.cn/goods.php?id=109

They decided to take the 121GW and put it in a bigger case, up the CAT rating, add true power measurement, motor measurement etc
Also, it's supposed to solve the DC offset issue by using separate AVC and DCV ranges.
The exiting line already had Bluetooth.
They kept stuff like the SD card logging, low burden, but dropped the 15V diode mode.
I had no idea they even had these existing designs.

That's a pity. This is one of the features I'm using a lot (checking LEDs and Zener diodes).
How much space is this part occupying on the board? Did they removed it for cost reasons?

[EEVblog]

That's a pity. This is one of the features I'm using a lot (checking LEDs and Zener diodes).
How much space is this part occupying on the board? Did they removed it for cost reasons?

I think it was going to be troublesome for their CAT IV rating, so probably decided to just drop it to be safe. This seems to be a more "electrical" oriented meter. But it's spec is better than the 121GW, so 

[EEVblog]

There is a UEi DM525 with bluetooth and power measurement already ($260.00).
Is it the same 6000 count meter in a different case?

Yep. UEi is one of Kane's brands. Would be the same meter I'm sure.
So it's almost certain they will sell this new one in the US under the UEi brand.

[2N3055]

So what's the deal with this new meter?
As I said, it "just appeared", I had absolutely no input to it nor knowledge of it. If you want to know why they did it, it seems like they want to extend their 500 series line with a higher end meter. Predominately sold in China I believe, but could be in other markets.
http://www.kanetest.com.cn/category.php?id=36
http://www.kanetest.com.cn/goods.php?id=109

They decided to take the 121GW and put it in a bigger case, up the CAT rating, add true power measurement, motor measurement etc
Also, it's supposed to solve the DC offset issue by using separate AVC and DCV ranges.
The exiting line already had Bluetooth.
They kept stuff like the SD card logging, low burden, but dropped the 15V diode mode.
I had no idea they even had these existing designs.

That's a pity. This is one of the features I'm using a lot (checking LEDs and Zener diodes).
How much space is this part occupying on the board? Did they removed it for cost reasons?

I have Metrix meter that has normal and zener mode (27V /10 mA) in diode test mode..
I use it all the time. I do a lot of LED displays and it allows me to test full segment of 5 serialy connected LED in one go..
I wouldn't want to give up that function..
It's a shame they dropped that, that was, to me and my work, more important than low dropout...