EEVBlog 121GW Discussion thread

[fboehle]

You are missing something. Multimeter specifications always refer to the ranges - not to currents or voltages you are measuring. So this table is talking about the 50uA to 10A ranges.

Thanks amspire, that makes sense and it is what I see in the manual for my fluke, but what I still don't get is, why is the range specified with the lower value, so the 5mA value, when it can measure down to 500uA?

Ranges on multimeters are always specified with the upper limit. The lower limit is always 0. So with the 5V range you can measure from 0V to +-5V. But to get a meaningful measurement, you need to have enough resolution to discern values at the lower end. A 50000 count DMM, like this one, will have a resolution of 0.0001V or 100 uV on the 5V range. So you can measure only discrete values from 0 to +-5V in 100uV steps.

[IanB]

Thanks amspire, that makes sense and it is what I see in the manual for my fluke, but what I still don't get is, why is the range specified with the lower value, so the 5mA value, when it can measure down to 500uA?

Please see my reply from above, reproduced below.

The table is really listing each of the independent ranges and their attributes, like this:

Range	Resolution, Accuracy	Burden Voltage
50 µA	1 nA, ±1.5%+15	100 µV/µA
500 µA	10 nA, ±1.5%+15	100 µV/µA
5 mA	0.1 µA, ±0.25%+5	2 mV/mA
50 mA	1 µA, ±0.25%+5	2 mV/mA
0.5 A	10 µA, ±0.75%+15	0.03 V/A
10 A	1 mA, ±0.75%+15	0.03 V/A

As per usual, you would pick the lowest range suitable for the value you wish to measure.

[tpw_rules]

I've made a patch which removes that mode/range change delay while autoranging, but I can't test it without a meter. I'm now wondering if anybody would be willing to sell me their meter for testing purposes?

If you upload the firmware file then we can test it.
I'd get you a meter, but we only have two production units left here.

Sure, as long as I'm not responsible for any possible bodily harm as a result And thanks for the note, I do understand you need to keep those. But I leave the country in a month and I'm worried I won't get a meter before then as I'm in the US group. I'd really like one to continue hacking on, it's been fun so far.

For the patch, I just made the autorange routine ignore the mode/range change delay if the last mode/range change was caused by autoranging. It might just oscillate wildly, who knows! If it does work, it could more than halve autorange time.

[EEVblog]

I've made a patch which removes that mode/range change delay while autoranging, but I can't test it without a meter. I'm now wondering if anybody would be willing to sell me their meter for testing purposes?

If you upload the firmware file then we can test it.
I'd get you a meter, but we only have two production units left here.

Sure, as long as I'm not responsible for any possible bodily harm as a result And thanks for the note, I do understand you need to keep those. But I leave the country in a month and I'm worried I won't get a meter before then as I'm in the US group. I'd really like one to continue hacking on, it's been fun so far.

For the patch, I just made the autorange routine ignore the mode/range change delay if the last mode/range change was caused by autoranging. It might just oscillate wildly, who knows! If it does work, it could more than halve autorange time.

Works! 
I compared UEi's v1.04 and it's only a smidgen slower, not even half a second.

[ChrisG]

I've made a patch which removes that mode/range change delay while autoranging, but I can't test it without a meter. I'm now wondering if anybody would be willing to sell me their meter for testing purposes?

If you upload the firmware file then we can test it.
I'd get you a meter, but we only have two production units left here.

Sure, as long as I'm not responsible for any possible bodily harm as a result And thanks for the note, I do understand you need to keep those. But I leave the country in a month and I'm worried I won't get a meter before then as I'm in the US group. I'd really like one to continue hacking on, it's been fun so far.

For the patch, I just made the autorange routine ignore the mode/range change delay if the last mode/range change was caused by autoranging. It might just oscillate wildly, who knows! If it does work, it could more than halve autorange time.

Works! 
I compared UEi's v1.04 and it's only a smidgen slower, not even half a second.

NICE!!!! 

[FrankBuss]

The company should hire tpw_rules. Pretty amazing to hack the binary without the source code and not even a meter for testing. Imagine what he could do if he would have the hardware and the source code

[EEVblog]

The company should hire tpw_rules. Pretty amazing to hack the binary without the source code and not even a meter for testing. Imagine what he could do if he would have the hardware and the source code

Indeed, thoroughly impressed! 

[AgiRigSig]

Wow, I am deeply impressed. As Frank already wrote,  UEI should hire tpw_rules 

[mikeselectricstuff]

I've made a patch which removes that mode/range change delay while autoranging, but I can't test it without a meter. I'm now wondering if anybody would be willing to sell me their meter for testing purposes?

If you upload the firmware file then we can test it.
I'd get you a meter, but we only have two production units left here.

Sure, as long as I'm not responsible for any possible bodily harm as a result And thanks for the note, I do understand you need to keep those. But I leave the country in a month and I'm worried I won't get a meter before then as I'm in the US group. I'd really like one to continue hacking on, it's been fun so far.

For the patch, I just made the autorange routine ignore the mode/range change delay if the last mode/range change was caused by autoranging. It might just oscillate wildly, who knows! If it does work, it could more than halve autorange time.

Works! 
I compared UEi's v1.04 and it's only a smidgen slower, not even half a second.

It's clearly doing some stuff it doesn't need to though - you see some intermediate displays during ranging

[ChrisG]

I've made a patch which removes that mode/range change delay while autoranging, but I can't test it without a meter. I'm now wondering if anybody would be willing to sell me their meter for testing purposes?

If you upload the firmware file then we can test it.
I'd get you a meter, but we only have two production units left here.

Sure, as long as I'm not responsible for any possible bodily harm as a result And thanks for the note, I do understand you need to keep those. But I leave the country in a month and I'm worried I won't get a meter before then as I'm in the US group. I'd really like one to continue hacking on, it's been fun so far.

For the patch, I just made the autorange routine ignore the mode/range change delay if the last mode/range change was caused by autoranging. It might just oscillate wildly, who knows! If it does work, it could more than halve autorange time.

Works! 
I compared UEi's v1.04 and it's only a smidgen slower, not even half a second.

It's clearly doing some stuff it doesn't need to though - you see some intermediate displays during ranging

Indeed Mike next to that I'm wondering if the v1.04 version can not be released to this group to try, test and give feedback.

[bicycleguy]

The company should hire tpw_rules. Pretty amazing to hack the binary without the source code and not even a meter for testing. Imagine what he could do if he would have the hardware and the source code

NO !   NO !  NO !     Don't let UEI steel him.  tow_rules should stay on the open source side and help us to not only get a more awesome meter but understand how it works!  I am really impressed

[Candid]

I am having problems with connecting the 121GW app from dave2. I did no get any data shown in the app up to now. Most time it even does not connect.

I first run bluetooth and connect to the 121GW then I start the app. Sometimes when I click on refresh I can see the 121GW. Only one time it was able to connect (but no data shown, only white screen). Most time it says "connecting..." but never does.

The other app "EEVBlog 121GW" sometimes connects successfully and shows some values but sorry, it's so ugly.

/EDIT:
Now I got it running for one time but I think I am missing some data on the screen?

[plexus]

Unforunately I immersed myself in the Apple eco-sh*thole starting in 1981. So I have macOS and iOS crap now. Eventually I will migrate away from all that.

But for now, where can I find updates on iOS/macOS software for the 121GW? I found the UEI iOS app and it works ok.

Is there somewhere where Dave is keeping us updated on software status? Or do I have to follow a thread?

Thanks!

[gnavigator1007]

 Acts like everything is fine set on volts with both leads plugged in A/mA

[tpw_rules]

Acts like everything is fine set on volts with both leads plugged in A/mA

Strange.  Maybe someone missed an OR statement.  Just an added bit of info, both the Fluke 189 and Brymen BM869s will fault out under this condition.

Yup, they missed it. Code is here. v0 is 0 if nothing's plugged in, 1 if mA is, 2 if A is, and 3 if both. They assume everything is OK if 0, or if 3. Maybe the hardware won't do the correct thing in case both are plugged in so they didn't check. I don't really understand how it's sensing a plug.

[bicycleguy]

...
Yup, they missed it. Code is here. v0 is 0 if nothing's plugged in, 1 if mA is, 2 if A is, and 3 if both. They assume everything is OK if 0, or if 3. Maybe the hardware won't do the correct thing in case both are plugged in so they didn't check. I don't really understand how it's sensing a plug.

From the schematic it looks like the mA and A input terminals are physically split with part pulled up to Vdd through ~30M res.  Inserting a lead shorts the split to the respective amps shunt to ground and op-amps sense and condition signal to the STM.  Just my speculation though, my meter arrives in March

[Candid]

Just tested it. AUTO DC+AC mode and I supplied about 25Vdc and it hunts. Raised voltage to about 44Vdc and it reads correctly. Lowering the DC voltage and it hunts again.

It looks like all pre-production errors are still present in the first batch of production meters of the 121GW. Even my crappy UNI-T UT71E is doing a better job in all of the discussed bugs.

I like to hear something soon from Dave how they will go on with the production meters of the early adopters... 

[ChrisG]

I use the AC+DC mode.  On the pre-production meter, this never worked very well.  If you wanted to try something very simple, switch the meter to AC+DC.  Attache the two leads normally (volts and common).   Now attach a DC supply and set it between 5 and 30 volts.  Does the meter just continue to hunt?   If it does, take the supply to 40-50 volts.  Does it now read correctly?    If it does, try lowering the voltage is see if it again starts to hunt.     Surely the released meters AC+DC mode works.

Hi Joe, not sure if what I did was right but I put it in AUTO DC+AC. Connected to my  EEZ H24005 power supply dialed in 25V (2mA current limit) and it displays it at 24.992 volt. on 5V it displays 5.000 volt at 40V it displays 39.989 on the meter. Apart from the still slow update rate it does not hunt in my opinion. Assuming the hunting is going back and forth and not getting a fix?

[Candid]

Are you both using the same firmware? 

I have the 1.02 with the auto range patch installed and I can reproduce the exact same behavior as you showed in the video with the pre-production meter.

I made some quick pictures without tripod. Hope they are ok to see the details:
http://www.abload.de/gallery.php?key=so5gQFPZ

[ChrisG]

Well it was not a cheap power supply at 500€ but will try with a 9V battery then later. I’ve so far not se3n what you show in your viceo. Anyone else?

[ChrisG]

Are you both using the same firmware? 

The pre-production meter would lock in depending on the AC and DC components.  If you have a cheap power supply with a lot of ripple for example, the meter may actually read correctly.   

V1.02 original (no autoranging patch)

[prof]

Just want to add that rotary switch wobble issue exists also with my meter (EU shipped). https://youtu.be/pjaWWMoPMsE
Is this same for everyone or only part of the already shipped meters?

Mine's the same. Not worried about that though.

[ez24]

Regarding the switch.  It seems like "you can't have your cake and eat it to" issue.

Isn't one of the selling points is that it can be turned with one hand?

My AN8008 switch is tight as it can be but it cannot be turned with one hand unless it is tied down.  Personally I like the one hand use and I am experimenting tying down the AN8008 (zip ties work the best so far).

So far no one has said that if there was no wobble, if it could or not be used with one hand.

[Candid]

First, thank you for taking these pictures!  Don't tell me that's a section of solder stuck to the bottom of the spring??

No it's part of the spring. I already re-soldered it.

Did you notice what appears to be metallic contamination around your pads?  It would be nice to get a better shot of this area with a microscope or macro lens.

Maybe next week or someone else can have a closer look on his meter.

I don't like that you are already seeing what appears metallic dust this early.  Maybe it's something in the lighting.

I did not use any flash, only room light (very strong cold LED at the ceiling and warm LED on the bench) what is not the best for taking neutral pictures. I was surprised myself to see that much dust after only some turns. I may have a second nearer view if I find some time the next days. Hopefully someone else can make some pictures to compare.

[KNSSoftware]

Isn't one of the selling points is that it can be turned with one hand?

So far no one has said that if there was no wobble, if it could or not be used with one hand.

If so, probably only after Dave realised early on that is was never going to be as stiff as the BM235 (which was a selling point about how stiff it was, and any shootout would get extra point for stiffness), and quickly turned a negative into a positive.  I think we underestimate how good he is at the marketing, and his own down playing of this skill, is a key part.  I would bet, if he could have got them to make it as stiff, he would have.