EEVBlog 121GW Discussion thread

[IanB]

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?

Again, it adds complexity and cost, to what purpose? What is the point?

Cell phones get charged every few days, so convenient recharging is relevant.

Multimeters get recharged every few months, maybe once a year. So what problem does a built-in rechargeable battery solve?

[tautech]

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?

Again, it adds complexity and cost, to what purpose? What is the point?

Cell phones get charged every few days, so convenient recharging is relevant.

Multimeters get recharged every few months, maybe once a year. So what problem does a built-in rechargeable battery solve?

Overall size and weight especially with lithium ion.

Joe Smith did some DMM logging tests with Bluetooth and it certainly can chew up batteries whereas if a DMM was logging while parked in an inductive charging cradle long term battery live would no longer be part of the picture.

Dave might like to think about a R2 version implementing these sorts of design features.

[IanB]

Joe Smith did some DMM logging tests with Bluetooth and it certainly can chew up batteries whereas if a DMM was logging while parked in an inductive charging cradle long term battery live would no longer be part of the picture.

That's true, but...I am forced to wonder if a combination of "sensitive measuring instrument" and "externally imposed inductive field" would be a good idea?

I am inclined to suspect it would be a shielding nightmare.

[IanB]

BTW, I have logged for hours at a time with my favorite logging meters and not had any concerns about battery drain, even though using a 9 V battery.

It's probably not the logging that's expensive, but the Bluetooth.

[EEVblog]

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?

No point when your meter has 500+ hours battery life, and you can change the batteries available anywhere.

[VEGETA]

when will 121gw meters be available again? how much total price to Jordan?

Also what is the difference in performance between it and the brymen one?

[Brumby]

To all those who missed the point on safety I was trying to make:   

The safety concern is one where you have a breach in the isolation of the meter for a charging port.  Only this response addressed that:

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?

Whether any efforts along this line are worth the effort, however, is another question.

[EEVblog]

After quite some R&D and testing, we have decided to drop the proposed 500V VA range support.
All the existing 50V and lower ranges will be available.

[imk]

Lipo's, alkaline's, Nicad etc are all things of the past anyway.
TEN TIMES the energy density of the above and all you need is tea spoon of sugar to recharge them.
500 hr becomes 5000 hr and that's half a year of continues use, even electric car start to make sense :-)
https://vtnews.vt.edu/articles/2014/01/012213-cals-battery.html

[Messtechniker]

Well, most news on this sugar battery is from 2014,
with not much thereafter.  Problems? Busted? April fools?

[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?

No point when your meter has 500+ hours battery life, and you can change the batteries available anywhere.

I was thinking of very long datalogging sessions, and perhaps using a meter that is not so low-power to last 500+ hours.

[Scottjd]

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?

No point when your meter has 500+ hours battery life, and you can change the batteries available anywhere.

Is this 500 hours of battery life while actively logging to an SD card and broadcasting serial Bluetooth signals? I have a logging meter, it doesn’t get any battery life like a normal one does with a single 9V.

[Scottjd]

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

How would access to the SD card compromise safety?
Ok, potential loop grounding issue if plugged into a computer USB port while measuring mains voltage at the same time. Or like three meters I own the simple solution is serial put data to usb via two infrared making it completely iscolated from the ground in the USB of the computer.
After all, it doesn’t need to be USB 3.1 Gen 2 sleeeds at 10Gbs data transfer, it is just little lines of text being stored. If the micro processor had a little extra code it might be able to complete one of the oldest tasks besides computers have dkne for years besides a calculator, and compress this into a zip file making it 1/100th of the original size for faster transfer speeds.

Update: I just saw the comment you made to those who missed the point. I didn’t miss it, but I do have a $20 meter in my hand that does this type of isolation made by Digitek, it’s the DT-4000ZC
if a $20 meter can do this, I’m sure the effort can be that much extra?

[mikeselectricstuff]

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

How would access to the SD card compromise safety?

Because the DMM's 0V rail could be connected to several hundred volts

[Scottjd]

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

How would access to the SD card compromise safety?

Because the DMM's 0V rail could be connected to several hundred volts

Ok, I know I dropped a $20 meter for an example,but the fluke 289 works the same way. The receiving IR and PCB/Chip is not connected to the main DMM PCB at all, in fact it’s powered by the 5VDC from the USB port. So forgive me if I wrong, but I still don’t see how that would be possible.

[IanB]

Ok, I know I dropped a $20 meter for an example,but the fluke 289 works the same way. The receiving IR and PCB/Chip is not connected to the main DMM PCB at all, in fact it’s powered by the 5VDC from the USB port. So forgive me if I wrong, but I still don’t see how that would be possible.

Because the SD card does not have onboard power like a USB port, and so the SD card driver has to be powered by the meter's internal circuitry, which means there is an electrical path between the terminals of the meter and the SD card.

[Scottjd]

Ok, I know I dropped a $20 meter for an example,but the fluke 289 works the same way. The receiving IR and PCB/Chip is not connected to the main DMM PCB at all, in fact it’s powered by the 5VDC from the USB port. So forgive me if I wrong, but I still don’t see how that would be possible.

Because the SD card does not have onboard power like a USB port, and so the SD card driver has to be powered by the meter's internal circuitry, which means there is an electrical path between the terminals of the meter and the SD card.

Ok, apparently I missed the point. I thought we were talking about transferring data on the SD off the meter   different ways?
I’m over it.

[imk]

121GW battery life vs battery type.
As far as the 500 hr battery life claim is this for alkaline or NiCad and what mah rating
My camera packs up much earlier on nicad than on fresh alkaline as the static voltage is lower for NiCad's
Any 121GW test data for various battery chemistry yet?

[maukka]

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.

I did not think the Killawatt could read very low power levels. 

But a good (for a cheap) power meter like the Zhurui PR10 will do fine down to 5mA at 230V. Takes 0.1 watts to display power though.

HKJ's test http://lygte-info.dk/review/Power%20Zhurui%20Power%20Recorder%20PR10%20UK.html

[EEVblog]

121GW battery life vs battery type.
As far as the 500 hr battery life claim is this for alkaline or NiCad and what mah rating
My camera packs up much earlier on nicad than on fresh alkaline as the static voltage is lower for NiCad's
Any 121GW test data for various battery chemistry yet?

4.2V dropout voltage, approx 5mA consumption, you can do the math with whatever chemistry.
The spec is Alkaline.

[EEVblog]

Is this 500 hours of battery life while actively logging to an SD card and broadcasting serial Bluetooth signals?

No, logging is lower, but don't have accurate specs for that. SD drops it to a few hundred hours IIRC. Have not tested Bluetooth, but it's BLE at a low sample rate so shouldn't take much.

[coromonadalix]

would be nice to pop in something like this gadget :  http://www.icstation.com/dual-card-adapter-shield-micro-card-dual-system-switch-converter-raspberry-b2b3b-p-10868.html

or an flexible sd card extender , but you have to slot the casing either way ...

[imk]

Is this 500 hours of battery life while actively logging to an SD card and broadcasting serial Bluetooth signals?

No, logging is lower, but don't have accurate specs for that. SD drops it to a few hundred hours IIRC. Have not tested Bluetooth, but it's BLE at a low sample rate so shouldn't take much.

Either way this 121GW is way ahead of anything else i have found, the PeakTech 3440 only does 7hr on batteries when logging so not a solution at all.
121GW is definitely going to get best meter of the year award :-)

[Brumby]

Getting ready to print the shipping labels is my guess.

[imk]

121GW battery life vs battery type.
As far as the 500 hr battery life claim is this for alkaline or NiCad and what mah rating
My camera packs up much earlier on nicad than on fresh alkaline as the static voltage is lower for NiCad's
Any 121GW test data for various battery chemistry yet?

4.2V dropout voltage, approx 5mA consumption, you can do the math with whatever chemistry.
The spec is Alkaline.

Well quick math looks like a 2400 mah AA NiCd down to 10% charge will still run the 121GW, so still in the region of 500 hr run time.
3200 mah Ni-MH would real push the envelope, think two sets of these would be why for me to go :-)

No mention of a supply date yet, so makes me wonder if not some under the covers magic being worked out