EEVBlog 121GW Discussion thread

[Brumby]

I guess you'll finally be buying one these then Brumby!!!!!!!!!
Perhaps not? As you seem to know all Dave's intentions for this meter, both present and future, if you resist this bargain 20% off deal then maybe your holding off for a revised model?

Gee - you like riding me, don't you?

As for "knowing Dave's intentions", there's nothing I have said that anyone could not deduce - but because there are a lot of people who don't make that effort, I'll do it for them - you included, it seems.

As for my purchasing the 121GW or not, that has nothing to do with revisions.  It has everything to do with 2 quite specific reasons.  The first is that I do not have a specific need for the functions the 121GW offers.  My EEVblog BM235 and the other meters I have currently serve me more than well enough.  The second is that I do not have sufficient funds for such a discretionary purchase at this time.  However, should I find myself with such funds available, then I will go shopping.


There is one thing that should be understood .... I've been following the development of the 121GW from the moment Dave gave the first hints of such a project.  Excuse me if I've picked up a few details and have an opinion on some things.

[Brumby]

My guess is that Dave has stock on his shelves that needs to be turned into cash.  Stock on the shelf doesn't do anything but tie up capital.  It needs to be sold and new stock ordered for any business to survive.

Correct. I talked about this on the Amp hour the other month. I have to buy a lot of meters in one hit, and it's a huge amount of money, the last lot (plus other things) practically wiped out the companies cash reserve. So much so that I had to stop paying myself wages.

Not surprising to anyone with half an idea of how small business is challenged on a daily basis.  I don't have any secret communications, just common sense (sometimes  ).

[EEVblog]

Not surprising to anyone with half an idea of how small business is challenged on a daily basis.  I don't have any secret communications, just common sense (sometimes  ).

Or people could just listen to The Amp Hour 

[ggchab]

It's just a meter, there was some excitement because it was a kickstarter, but now it's a year and half later and it's now just another product in my store. That was inevitable.

To be totally honest, I would add "and because it was Dave's meter" 
Thank you for the clarification. I was hoping this would take more time but I understand.

A simple message like

I'm using 2.00 firmware at present and UEI have said we can release it, so expect it soon."

is good news 

[thinkfat]

I'm using the 1.54 software version, no problems with it. If 2.00 improves it even further - that will be brilliant!

[Brumby]

Fixes are still coming. I'm using 2.00 firmware at present and UEI have said we can release it, so expect it soon. Improvements are better and faster resistance and capacitance autoranging.

Well, that explains why there was no comment about the V1.61 FW some people had encountered.  No need to waste time with that when the new release was imminent.  (We just have an alert user base that picked up on that a week or two too early.)

[oliv3r]

Could someone please share calibration data? I lost it while messing up with the meter and not all ranges I can calibrate (like I don't have a high-voltage source for AC, for example). I know results won't be perfect, but it's fine

Check your PM for:
$ md5sum CAL.BIN
ca2b85fe5be9863f3b96db3cc925d419  /media/oliver/121GW/CAL.BIN

Since I can PM files, I'm sure you don't mind that it's base64 encoded

[joeqsmith]

After Dave's comments about reviving the toggle bot to repeat the switch life cycle testing, I offered to buy a couple of the new meters and run that test for them but no response and I have not heard anything else.

If I had a spare new thicker PCB meter to send you, I would.

I'm in no rush.   

Not surprising to anyone with half an idea of how small business is challenged on a daily basis.  I don't have any secret communications, just common sense (sometimes  ).

Or people could just listen to The Amp Hour 

If you pay attention, there are normally a few gold nuggets in those shows. 

[rthorntn]

Does anyone have any idea on how to source replacement probes?

[jancumps]

Does anyone have any idea on how to source replacement probes?

This is the model: Silicone test leads BL21S2-T4SC Brymen

[J-R]

Now, it seems that the "soufflé est retombé" as we say in French. I would like to be proven the opposite, but except a few apparitions of the multi-meter in some videos, enthusiasm seems to be gone, upgrades are no longer available, no more reaction from any Dave.

What "enthusiasm" do you want?
Want me to include an outro in every video plugging the meter?
It's just a meter, there was some excitement because it was a kickstarter, but now it's a year and half later and it's now just another product in my store. That was inevitable.
Fixes are still coming. I'm using 2.00 firmware at present and UEI have said we can release it, so expect it soon. Improvements are better and faster resistance and capacitance autoranging.

That's the biggest announcement about the 121GW I've heard since I bought it a year ago.  I'm enthusiastic about getting my hands on the new firmware.

[BrianG61UK]

I just received my 121GW.

I don't understand the reasoning behind "Low Z".

Having an optional internal load on a voltage range makes sense, but why fixed on a high voltage range and not auto ranging? And why AC only?

I just don't get it.

[0xdeadbeef]

"Low Z"  is typically meant for "ghost voltage" on mains.

[Cnoob]

https://www.ebay.co.uk/itm/Brymen-Silicone-Gold-Plated-Test-Leads-Probes-for-Multimeters-CAT-IV-1000V/171162377470?hash=item27da129cfe:g:uSQAAOxyTjNShpch&frcectupt=true

I get my Brymen Probes from here plus other test leads all good quality and quick and reliable delivery.

[BrianG61UK]

"Low Z"  is typically meant for "ghost voltage" on mains.

But wouldn't it make sense to allow it to be used for other things like testing batteries?

In most high impedance "ghost" mains voltage cases isn't one more interested in measuring the current anyway (measure with a few kohm R in series so no chance you blow a fuse somewhere)?

In the low impedance case (eg two earths/grounds that have a voltage between them) you can just use normal voltage range.
 

[0xdeadbeef]

But wouldn't it make sense to allow it to be used for other things like testing batteries?

Theoretically yes, but the current would be still pretty low for a battery. E.g. the Fluke 117 has ~3kOhm resitance in LoZ mode, so a 1.5V cell would cause a current of 500µA. That's probably not enough to be useful for battery testing.

In most high impedance "ghost" mains voltage cases isn't one more interested in measuring the current anyway (measure with a few kohm R in series so no chance you blow a fuse somewhere)?
just use normal voltage range.

Ghost voltages are created by capacitive coupling (no current flowing). With the typical multi MOhm resistance, you can measure voltages like e.g. 75V that seem to be dangerous. When measuring in LoZ mode, the current over the e.g. 3kOhm resistor is enough for the ghost voltage to disappear.

[BrianG61UK]

But wouldn't it make sense to allow it to be used for other things like testing batteries?

Theoretically yes, but the current would be still pretty low for a battery. E.g. the Fluke 117 has ~3kOhm resitance in LoZ mode, so a 1.5V cell would cause a current of 500µA. That's probably not enough to be useful for battery testing.

In most high impedance "ghost" mains voltage cases isn't one more interested in measuring the current anyway (measure with a few kohm R in series so no chance you blow a fuse somewhere)?
just use normal voltage range.

Ghost voltages are created by capacitive coupling (no current flowing). With the typical multi MOhm resistance, you can measure voltages like e.g. 75V that seem to be dangerous. When measuring in LoZ mode, the current over the e.g. 3kOhm resistor is enough for the ghost voltage to disappear.

You think that if you put AC across a capacitor no current flows?

I thought we were all engineers in here.


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[0xdeadbeef]

You think that if you put AC across a capacitor no current flows?

Let's not start nitpicking. It's quite obvious that I intended to explain that ghost voltages are not caused by inductive coupling (i.e. through a current) but by capacitive coupling.

I thought we were all engineers in here.

I thought we were here to help each other, not to be smarty-pants.

[Brumby]

You think that if you put AC across a capacitor no current flows?

You seem to be missing some basics here...

For the ghost voltage situation, putting a DMM with a 10M (or higher) input impedance across it is not going to load the voltage down a lot.  You could easily measure 100VAC which might prompt you to start chasing down a fault that simply does not exist.  The simple answer is to put an appropriate load across the measured points and then read off the voltage.  Know your load and know your voltage means you know your current.

What is of most interest here is not the actual current that flows but the voltage you read when the circuit is under this load.  Because the capacitance that allow these voltages to exist is so low, the loading provided by a meter with a Lo-Z range often drops the voltage measurements down to zero - or close to.  When this happens, your confidence that the circuit measured does not have dangerous power behind it rises dramatically.

Of course, if you still measure 100VAC (or whatever) on a Lo-Z range, then you do have something to chase down.

I thought we were all engineers in here.

This is not helpful.

Most of us here have, what I call, "engineering minds".  Some are qualified, some have experience, some have the drive and some, the ambition - but we all try and keep ourselves grounded in the way things work in the real world.  You seem to be resting on the pedant pedestal a tad.

So, let me ask you this question...
Say you measure 100VAC in the normal high impedance mode of a DMM - and then measure zero when you switch to the Lo-Z mode?  How much current is flowing?  Ohm's law gives a clear answer.

Of course, theoretically we know there must be some current flowing - but it's going to be one poofteenth of a gnat's wing - and as far as the real world is concerned, that is negligible (unless you're playing with atomic force microscopy or somesuch).

As a practical consideration, sometimes the theoretical needs to be properly understood - and put to one side.

[CDaniel]

LoZ is for AC and DC . When "engineering minds" work in real world will find many situations when a voltage in a circuit looks OK with a tipical high impedance multimeter , but it's not actually , because there is a fault and the circuit is just capacitive coupled or there is some high resistance conductive dirt somewhere ... For this is LoZ .
For example in a car circuit , you should check with LoZ or a light bulb if the fuses are OK , if not , a blown fuse can leave some conductive traces and you would be fooled with a normal multimeter .

[BrianG61UK]

LoZ is for AC and DC . When "engineering minds" work in real world will find many situations when a voltage in a circuit looks OK with a tipical high impedance multimeter , but it's not actually , because there is a fault and the circuit is just capacitive coupled or there is some high resistance conductive dirt somewhere ... For this is LoZ .
For example in a car circuit , you should check with LoZ or a light bulb if the fuses are OK , if not , a blown fuse can leave some conductive traces and you would be fooled with a normal multimeter .

Yes.
So why is it AC only on the 121GW ?

[BrianG61UK]

You think that if you put AC across a capacitor no current flows?

You seem to be missing some basics here...

For the ghost voltage situation, putting a DMM with a 10M (or higher) input impedance across it is not going to load the voltage down a lot.  You could easily measure 100VAC which might prompt you to start chasing down a fault that simply does not exist.  The simple answer is to put an appropriate load across the measured points and then read off the voltage.  Know your load and know your voltage means you know your current.

What is of most interest here is not the actual current that flows but the voltage you read when the circuit is under this load.

Most interest? Why?  The rules and regulations about how much leakage is safe quote currents not voltages across some vaguely defined non linear load.

[HKJ]

So why is it AC only on the 121GW ?

Why do you believe it is AC only?
My 121GW have no problems showing DC voltage in LowZ mode.

[HKJ]

Most interest? Why?  The rules and regulations about how much leakage is safe quote currents not voltages across some vaguely defined non linear load.

You need both voltage and current before it is dangerous and I am not sure LowZ is designed to show dangerous voltage, but more to show if there is power available.

[BrianG61UK]

So why is it AC only on the 121GW ?

Why do you believe it is AC only?
My 121GW have no problems showing DC voltage in LowZ mode.

That's odd. Mine showed nothing on a 6V battery.

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