EEVBlog 121GW Discussion thread

[EEVblog]

Only thing i would change if possible would be the ability to remove/swap  the micro sd card without taking the back off, a little hatch would be great and well if you do consider it

This has been mentioned before - but I believe the issue is one of safety.  The Cat ratings and safety design of the 121GW is based on the only access to the meter's circuitry being through the probe sockets on the front - which have been designed to certain standards.

To access the microSD card, you would be given access to the microSD card slot - which is connected to the meter's innards.  Such an interface would need very special consideration to be suitably rated - if, indeed, that were at all possible.  Since the microSD facility was a "fit in", the restriction on access in order to maintain safety and the Cat ratings is one that will (as I understand it) have to stand.

Yes, it's an issue of access safety.
I know it's a bit of a PITA, but it takes under 20 seconds to remove the boot, unscrew the cover and remove the SD card and insert into computer.
If you need more accessible data logging then I'd recommend a proper data logger. This is a multimeter first with some SD logging capability, not the other way around.
I guess you could always dremel a slot in the back perhaps?

[EEVblog]

Hey Dave, should I start checking my letterbox anytime soon for a delivery?
It must be getting very close by now for the Johnny B Goode shipment to be shipped.
Looking forward to playing with this meter sometime very soon 

The rest of the Great Scott backer will be shipped first.
We are close to a release solution, just dealing with a few last minute things, that's my job this morning.

[IanB]

Yes, it's an issue of access safety.
I know it's a bit of a PITA, but it takes under 20 seconds to remove the boot, unscrew the cover and remove the SD card and insert into computer.
If you need more accessible data logging then I'd recommend a proper data logger. This is a multimeter first with some SD logging capability, not the other way around.
I guess you could always dremel a slot in the back perhaps?

I would have imagined trying to have the SD card slot under the battery cover rather than having to open the whole meter to access it...?

[EEVblog]

I would have imagined trying to have the SD card slot under the battery cover rather than having to open the whole meter to access it...?

The SD card is under the battery cover (with machine screws, so won't wear out), but like many meters you have to remove the rubber boot to access the battery compartment.
I've timed it, it took me less than 20 seconds to access.

[VEGETA]

Why don't you make the SD card slot from the side like laptops? just a hole\slot in the side of the multimeter and it will be perfect. The holster will hide and protect it.

[Cliff Matthews]

Why don't you make the SD card slot from the side like laptops? just a hole\slot in the side of the multimeter and it will be perfect. The holster will hide and protect it.

But it's not in the same compliance category as a laptop, so it wouldn't have passed standards testing.
(EC 60950 talks about "Emission of flame or expulsion of molten metal")

[bitwelder]

I guess you could always dremel a slot in the back perhaps?

Would one of those WiFi-enabled SD cards work?

[mtdoc]

Why don't you make the SD card slot from the side like laptops? just a hole\slot in the side of the multimeter and it will be perfect. The holster will hide and protect it.

But it's not in the same compliance category as a laptop, so it wouldn't have passed standards testing.
(EC 60950 talks about "Emission of flame or expulsion of molten metal")

IIRC the Mooshimeter had the same issue with testing and its SD card slot and also opted for a slot that required opening the case to access.

[EEVblog]

I guess you could always dremel a slot in the back perhaps?

Would one of those WiFi-enabled SD cards work?

It's micro SD, do they even make those?
And no idea if it would work.

[Mr.B]

IIRC the Mooshimeter had the same issue with testing and its SD card slot and also opted for a slot that required opening the case to access.

Correct.
The one I have has thinner indented plastic molding where the slot was in the original design.
The guy who designed the meter had to change the injection mold to comply with the required safety standards.
However, the end user can easily snap out the plastic to make a slot if they wish - at their own risk of course.

[mtdoc]

IIRC the Mooshimeter had the same issue with testing and its SD card slot and also opted for a slot that required opening the case to access.

Correct.
The one I have has thinner indented plastic molding where the slot was in the original design.
The guy who designed the meter had to change the injection mold to comply with the required safety standards.
However, the end user can easily snap out the plastic to make a slot if they wish - at their own risk of course.

Yep. James had to change it. The result was something that passes testing but can be easily modified for easier SD card access.

I don’t know if something similar could have been done with the 121GW - maybe not since a large OEM is involved. But I agree with Dave that it’s not that hard to get to the SD slot in any case.

[EEVblog]

I don’t know if something similar could have been done with the 121GW

It wasn't. The SD card was added after the case molds had been made.

[imk]

Oh Dave, i wonder if this SD issues is getting more attention than it deserves?

I  need (not urgently) a new multimeter as my main one is on the blink so thought i'd treat myself to a nice new one as landmark birthday coming up.
Friend wants me to do some battery performance comparisons plus i want to do some solar cell output checks so data logging via MM seems the way to go.
Bust my brain for a week going around the reviews/shops looking for what I thought  i wanted which was a wired solution (RS232/USB).
Then a moment of clarity dawned, a MM with 4xAA built in recording/logging at a price the fits my needs+budget equation that doesn't need wires WOW!
Much searching reveals one solution the 121GW, Dave when can i have one please?

I only mentioned the SD hatch as possible scenario "Can't find my USB dongle and Bugger I need to go to workshop for Screwdriver.
Please forget i ever mentioned it and if there's anything i can do to help you get the 121GW in the shops just ask as i'm retired and have time to help good projects like this :-)
Plus lots of C/C++ PC and embedded/PIC coding miles.
 
Ian
 

[VEGETA]

I wonder about something... Why don't mutlimeters come with rechargeable batteries such as Li-ion\Li-Po? with capability to charge it with micro USB plug.

I suspect that it won't pass tests for safety or so, but I need the correct answer.

[IanB]

I wonder about something... Why don't mutlimeters come with rechargeable batteries such as Li-ion\Li-Po? with capability to charge it with micro USB plug.

I suspect that it won't pass tests for safety or so, but I need the correct answer.

1) Most multimeters use so little power that rechargeable batteries are unnecessary
2) If you want to use rechargeable batteries with an external charger there is nothing to stop you
3) With a built-in rechargeable battery you are left unable to use the meter while the batteries are recharging, making this an inconvenient solution

[Brumby]

 4) Access for charging internal batteries would compromise safety - just as having external access to the internal microSD card would be on the 121GW

[HKJ]

4) Access for charging internal batteries would compromise safety - just as having external access to the internal microSD card would be on the 121GW

It is possible to work around that (A safety rated DC/DC converter).

[imk]

I wonder about something... Why don't mutlimeters come with rechargeable batteries such as Li-ion\Li-Po? with capability to charge it with micro USB plug.

I suspect that it won't pass tests for safety or so, but I need the correct answer.

Guess this is how you get around the safety issues of rechargeable MM
https://www.alibaba.com/product-detail/Rechargeable-Self-Restoring-LCD-Digital-Multimeter_60366637118.html?spm=a2700.7724857.main07.8.198777e4cV0KF7

[VEGETA]

4) Access for charging internal batteries would compromise safety - just as having external access to the internal microSD card would be on the 121GW

I think it is just an over concern. I don't think that there is anything bad gonna happen since we have tons of products with Li-ion batteries and are safe, same for SD card issue. But this is just my humble opinion... If there is an affordable good meter like 121gw but with rechargeable battery, I would buy it.

 

Guess this is how you get around the safety issues of rechargeable MM
https://www.alibaba.com/product-detail/Rechargeable-Self-Restoring-LCD-Digital-Multimeter_60366637118.html?spm=a2700.7724857.main07.8.198777e4cV0KF7

LOL... WTF! this is very nice although being stupid!

perfect workaround  Safety my ***

These probably followed ElectroBOOM advice: "Safety always comes second priority"

[HKJ]

Guess this is how you get around the safety issues of rechargeable MM
https://www.alibaba.com/product-detail/Rechargeable-Self-Restoring-LCD-Digital-Multimeter_60366637118.html?spm=a2700.7724857.main07.8.198777e4cV0KF7

Keysight has one DMM where you apply 24VDC to the probe input to charge, this means you have a huge external power supply.
I do not really know what I like best of these two solution.

[IanB]

If there is an affordable good meter like 121gw but with rechargeable battery, I would buy it.

Why would you buy it? What problem does it solve for you?

[ez24]

Guess this is how you get around the safety issues of rechargeable MM
https://www.alibaba.com/product-detail/Rechargeable-Self-Restoring-LCD-Digital-Multimeter_60366637118.html?spm=a2700.7724857.main07.8.198777e4cV0KF7

This meter has something I like : polyfuses

Why don't other meters use them?

[HKJ]

This meter has something I like : polyfuses

Why don't other meters use them?

One reason may be burden voltage, they have higher on resistance than fuses (At least the ones I have seen in multimeters).

They can probably not match a high quality fuse in safety either.

[Cliff Matthews]

DMM front-end design factors-in known resistance of fuses that recover well. Sadly, polyfuses may some undesirable specs.

[bitwelder]

Would some kind of inductive powering (like Qi charging) feasible in a safe way in a meter, if the receiving antenna is e.g. well inside the body of the instrument, like the battery compartment?