EEVBlog 121GW Discussion thread

[lowimpedance]

I re-checked with 1.10 and get the same results. Can someone confirm my measurements?
Why is the 121GW reading wrong in auto range/manual 5V range in this situation?

Can you reproduce the following measurements?
2.0V peak to peak sine wave 4kHz, No DC offset, duty cycle 50%. Both meters in AC mode. Firmware 1.07 on my 121GW with serial number EEVblog 000084

Auto mode on both meters, Fluke in highres mode:
121GW selects 5V range, reads 1.1133Vac
Fluke 28II selects 6V range, reads 0.7031Vac

manual mode on both meters:
121GW 5V range, reads 1.1133Vac
Fluke 28II 6V range, 0.7032Vac

121GW 50V range, reads 0.659Vac (and it looses the frequency measurement and displays 0.00kHz)
Fluke 28II 60V range, reads 0.663Vac

See the attached pictures.

 Conducted similar measurements and can confirm similar results with regard to the frequency display. I will post the results in the 121GW issues thread where it is more appropriate.
EDIT decided to post the results here after doing some more testing and I think its not actually any bugs as such and just more like the characteristics of the meter front end.
anyway test results below........

 Ok further to Candid's test I conducted a similar test of the AC range and secondary frequency display reading.
Results for: 2V p-p 4 kHz sine wave input (terminated into 50 .). My 121GW with firmware rev 1.10.
Other meters used in comparison where Fluke 87V and Fluke 8840a

Meters in Auto ranging.
121GW reads 0.7288V RMS and the secondary display show the frequency of 3.999 kHz.
Fluke 87V in hi res reads 0.7300V RMS
Fluke 8840a reads 0.7300V RMS

Meters set to manual range.
121GW on 5V
87V on 6V
8840 on 2V
All display the same as above as expected.

Meters set to next range up.
121GW on 50V,  The voltage reading starts at 0.701V RMS for around 3 to 5 seconds then drops to 0.682V RMS and at which point the secondary frequency display goes to all zeros.
Fluke 87V on 60V, reads 0.690V RMS.
Fluke 8840a on 20V reads 0.7299V RMS and on 200V range reads 0.720V RMS.

additional measurement on the 121GW 500V range reads 0.47V RMS at both 4 kHz and 500 Hz (secondary frequency display is at 0), just for fun  .

NB * Further measurements of the frequency reading display show that it has a threshold of just over ~1.1 V before the secondary display starts to read frequency correctly when manual ranging to the 50V range.

[Seppy]

I re-checked with 1.10 and get the same results. Can someone confirm my measurements?
Why is the 121GW reading wrong in auto range/manual 5V range in this situation?

Can you reproduce the following measurements?
2.0V peak to peak sine wave 4kHz, No DC offset, duty cycle 50%. Both meters in AC mode. Firmware 1.07 on my 121GW with serial number EEVblog 000084

Auto mode on both meters, Fluke in highres mode:
121GW selects 5V range, reads 1.1133Vac
Fluke 28II selects 6V range, reads 0.7031Vac

manual mode on both meters:
121GW 5V range, reads 1.1133Vac
Fluke 28II 6V range, 0.7032Vac

121GW 50V range, reads 0.659Vac (and it looses the frequency measurement and displays 0.00kHz)
Fluke 28II 60V range, reads 0.663Vac

See the attached pictures.

Regarding the 50V range the loss of the frequency measurement is expected, it is the wrong range for that reading and the threshold doesn't kick in for that range as it is higher.
The 5V range does appear wrong on your meter but we haven't been able to reproduce it, it could be an issue with your unit in that range.
Can you confirm that the Hz range functions correctly on your meter?

Can you also test the same range with 400Hz?

[EEVblog]

With regards to the requested 500V/5A (250VA) VA power mode. It is possible to add this (with some sacrifice in other ranges), and we have tested a solution.
But now I'm I am wondering whether or not it's actually worthwhile?
After all the meter is only capable of measuring VA and not true Watts, as the chipset does not have the phase measurement capability.
With this in mind, how useful is VA measurement in AC mode to people without a true Watts capability?
Note, that adding AC VA ranges drastically increases the number of factory calibration points required for every range added, and we are trying to minimise these ranges were possible.

SNAP POLL:
1) Should the 500V AC VA mode be added at the expense of a few of the other lower ranges?
2) Is AC VA mode even useful to people? (obviously the DC VA mode is)

[Fungus]

No.

PS: What would be the "sacrifices in other ranges"?

[HKJ]

1) Should the 500V AC VA mode be added at the expense of a few of the other lower ranges?
2) Is AC VA mode even useful to people? (obviously the DC VA mode is)

1) I believe this meter is for electronic, i.e. it needs the lower ranges.
2) I do not see the point in AC VA modes, I want real Watt.

The reason I bought the meter was the low burden voltage and the high diode test voltage, but if I start using it generally it will be for electronic.

[IanB]

1) Should the 500V AC VA mode be added at the expense of a few of the other lower ranges?
2) Is AC VA mode even useful to people? (obviously the DC VA mode is)

No. This is an electronics meter. There are more dedicated tools available for AC power measurements that can also do Watts and power factor. It is not worth sacrificing lower ranges for this.

[EEVblog]

Sorry for the confusion.
I was talking about the 500V range at lower currents.
i.e. We plan to add only a 500V/10A range, not 500V/uA/mA ranges as well, that would add far too extra many factory calibration points.
We are having accuracy problems with the 500V/10A AC VA mode at the more outside edges of the voltage and current values, they are not sure if they can fix this.
I'm now asking if it's worthwhile having the 500V/10A AC VA range at all? I can't personally, but I'm not really an AC industry guy.

[imk]

Hello,
As don't have the 121GW yet was wondering before ordering if the PC Gui logging software will work with one of these please:
https://www.overclockers.co.uk/asus-usb-bt400-bluetooth-4.0-usb-adaptor-nw-076-as.html
Many thanks

[EEVblog]

Hello,
As don't have the 121GW yet was wondering before ordering if the PC Gui logging software will work with one of these please:
https://www.overclockers.co.uk/asus-usb-bt400-bluetooth-4.0-usb-adaptor-nw-076-as.html
Many thanks

Any 4.0 adapter that supports BLE mode should work.

[imk]

Hello,
As don't have the 121GW yet was wondering before ordering if the PC Gui logging software will work with one of these please:
https://www.overclockers.co.uk/asus-usb-bt400-bluetooth-4.0-usb-adaptor-nw-076-as.html
Many thanks

Any 4.0 adapter that supports BLE mode should work.

Hello Dave and many thanks for the prompt reply.
So i have been driving me-self nuts trying to find a new MM for a week now and think this really fit my needs.
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, it could i guess a retro fit back for those lucky people that already have one.
BTW i have contacted Welectron re when they may have some but was wondering if you had a waiting customer list i could be added to please, i can pm you my email if you wish?
Again many thanks imk

[imk]

1) Should the 500V AC VA mode be added at the expense of a few of the other lower ranges?
2) Is AC VA mode even useful to people? (obviously the DC VA mode is)

1. My needs are electronic so no need for 500v ac
2. Would AC VA (Watts) be useful for audio amplifier output power measurements? if so then maybe useful to me.

[IanB]

I'm now asking if it's worthwhile having the 500V/10A AC VA range at all? I can't personally, but I'm not really an AC industry guy.

This is how I understood the question, and how I answered it. It doesn't seem worth sacrificing other capabilities for this.

[bicycleguy]

With regards to the requested 500V/5A (250VA) VA power mode.

Is that 2500VA?

It is possible to add this (with some sacrifice in other ranges), and we have tested a solution.

What is the sacrifice exactly?  Isn't the next range down 500mVAC.

But now I'm I am wondering whether or not it's actually worthwhile?
After all the meter is only capable of measuring VA and not true Watts, as the chipset does not have the phase measurement capability.
With this in mind, how useful is VA measurement in AC mode to people without a true Watts capability?

Doe's this mean Joe noob (ie me) looking around for things to measure won't be able to look at all my energy wasting 110VAC stuff.  I think my new fangled utility meter bills me measuring only VA? 

[HKJ]

Doe's this mean Joe noob (ie me) looking around for things to measure won't be able to look at all my energy wasting 110VAC stuff.  I think my new fangled utility meter bills me measuring only VA?

Usual it is Watt the utility meters are measuring. VA is just current multiplied by voltage, i.e. you can get a very good estimate of VA by measuring the current and multiply by 120.

[IanB]

Doe's this mean Joe noob (ie me) looking around for things to measure won't be able to look at all my energy wasting 110VAC stuff.  I think my new fangled utility meter bills me measuring only VA?

You are better using a Kill-A-Watt (original, or one of the many clones) device for this application. It will report both true power and power factor, and will have a built-in totalizing feature. It is also much safer to plug into a power socket without dangling wires or test leads.

Your utility meter measures actual power and you get charged for actual power. You do not get charged for VA.

[1anX]

I bought the meter for electronics and like others have indicated the low burden voltage and higher zener test voltages appealed to me.
I have other meters for mains AC voltages and currents!

[Candid]

The 5V range does appear wrong on your meter but we haven't been able to reproduce it, it could be an issue with your unit in that range.
Can you confirm that the Hz range functions correctly on your meter?

Can you also test the same range with 400Hz?

HZ range functions well up to about 720kHz in the Hz mode, and up to 680kHz in V mode on the second display (with a sine 2Vpp).

I tested with 400Hz sine 2Vpp and get the same wrong voltage measurement at 5Vac (auto) range mode (1,1xxx Vrms). 50Vac manual mode gives me again the correct measurement.

[EEVblog]

Is that 2500VA?

5000VA actually, 10A capable.

What is the sacrifice exactly?  Isn't the next range down 500mVAC.

The next range down is 500VA, but it's a 50V range, not 500V, that's what I'm saying, there is only one 500V range and that is 10A.

Doe's this mean Joe noob (ie me) looking around for things to measure won't be able to look at all my energy wasting 110VAC stuff.  I think my new fangled utility meter bills me measuring only VA?

You should not be using a multimeter like this for your appliances, just but a cheap Kill-A-Watt unit that measures proper W and VA power.
Most utilities will charge in W, not VA for residential customers, but that varies depending upon the country and utility company.

[Cliff Matthews]

This $11 inductive meter can be handy enclosed on the receptacle end of a DIY extension cord. Here it is in action.

[Elasia]

AC fruit cake checking in

I also say no, there are more purpose built devices for this on both the low end as above and high end as well like this http://en-us.fluke.com/products/power-quality-analyzers/fluke-345-clamp-meter.html i got at work.

Or can even be made quickly and cheap but who does that when China does it for you these days

As others already said, i think the world of a good electronics meter built for that purpose.. dont spoil the goods trying to be good at to many different things.

[geekGee]

The meter is EEVBlog branded and I believe the first "E" stands for "electronics". 

That's why I ordered one anyway.

[Seppy]

I was thinking of the spurious VA values. We no longer get these as it's been (as far as we can tell) fixed in software. So if spurious values are being seen, maybe that's a possible cause?
But if it's a checksum thing, then forget I said it.
But as I believe David (seppy) has said, we are no longer getting corrupted data, and hence no more checksum errors.

How could the range switch cause invalid xor checksums?

I don't see spurious VA values as in the early versions of the firmware.

With V1.10 I still see wrong voltage and current displays in certain parts of the measuring range, I see a spurious wrong decimal point in current display and I see wrong range display (A instead of mA) in the current display. All of this in DC VA-mode.

Apart from that the displayed values are consistently wrong.

I guess the invalid checksums must then be some electrical problem in my meter if no one else can see them.

As there seems no way to debug it further, I can't help you there.

Update has been released to the app stores, likely hasn't updated on both yet but these issues should all be resolved now, we also have a new firmware version which will be resolving one of the other issues (when the voltage in VA mode is above 32767 approximately, this firmware update hasn't been released, this issue was a packet issue not a app issue so for those values you'll need to wait for the next firmware update).

[Brumby]

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.

Using the Bluetooth facility is probably going to be a better bet for the sort of things I suspect you are contemplating.

[1anX]

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 

[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?