Author Topic: EEVblog 121GW Multimeter Issues  (Read 560194 times)

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Offline beanflying

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Re: EEVblog 121GW Multimeter Issues
« Reply #1275 on: January 04, 2021, 02:42:45 pm »
At this time of the year I suspect Dave will be doing family things.

Other than that start by reading this https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-issues/msg2792850/#msg2792850

There was a small batch this issue may have happened with and a bit of a search would have found it.
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Offline tester

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Re: EEVblog 121GW Multimeter Issues
« Reply #1276 on: January 04, 2021, 02:55:16 pm »
Thanks a lot for lightning fast response.
I did register some complaints about the terminals (joe smith @yt) perhaps others. Don't recall the details - haven't been on the topic since first occurence half y. ago.
BTW - my SN 1808078XX is out of the range suspected to be problematic.
 

Offline J-R

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Re: EEVblog 121GW Multimeter Issues
« Reply #1277 on: January 04, 2021, 07:07:28 pm »
Do you have the UEi or Brymen test leads?
 

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Offline tester

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Re: EEVblog 121GW Multimeter Issues
« Reply #1279 on: January 04, 2021, 07:55:19 pm »
Just now I noticed on the pic from 2020-06-12, the mA/uA seems to be cracked already in place where the metal terminal ends. Unfortunately its out of focus..
The forces required to insert/remove the leads are nothing out of ordinary.
On old Vichy VC97 test leads have been 3-5x more stiff. They require considerable force especially on the way in.

The 121GW terminals are from kind of fragile hard plastic which seems to have tendency to shatter rather than deform slightly. The A/500mA was superglued and holds since, but I feel a bit uneasy when attaching and detaching leads..
 

Offline Mr. Wizard

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Re: EEVblog 121GW Multimeter Issues
« Reply #1280 on: January 05, 2021, 08:16:03 pm »
I wanted to find out whether the meter can be used with lithium batteries instead of standard cells or not.
Problem with lithium cells ist the higher voltage. 4 lithium cells have up to 7.7V when they come out of the package. After a short time the voltage goes back to approximate 6.6V and stays a long time at this value.
Problem or not?
I could not find any hint to this question, so I started to explore the schematics.
First it looked good, all internal voltages came from low drop regulators.
+4V, VDD(3.3V) analog supplies and VDD_P  (3.3V) for the 15V booster and the CPU.
So, no problem at all, none of the voltages can go to high.
But wait, what is that?
The voltage reference, ZD1, a ADR3412 reference regulator is connected directly to B+ via R94, a 0 ohm resistor. B+ is the battery voltage. And this is a problem in my opinion. According to the datasheet the input voltage range of the ADR3412 is 2.3V..5.5V, the absolute maximum is 6V.
That means even with alkaline batteries the voltage is above the input range and with new alkaline batteries also above the absolute maximum. With lithium cells it is way off from the allowed input voltage.
Populate R12 instead of R94 will supply the reference with +4V, so no problems in this configuration. But R94 is populated, not only in the schematics. I have checked this in my meter and actually R94 is populated. I will remove R94 and place it in the R12 position.I cannot understand why the reference is connected to B+, that makes no sense for me. Is this really a design flaw or did I overlook something?
I’ve been purging my lab of alkaline batteries, which keep leaking, and replacing them with Energizer lithium cells. The only thing I have that can’t handle lithiums is my 121GW, where its ADR3412 will be fed too high a voltage from fresh lithiums. I figured I might as well move the 0-ohm jumper from R94 to R12 to make the meter lithium-safe, as long as that’s not going to cause any other problems.

Before making the mod, I wanted to check on the forum. I’ve been pondering why the jumper was on R94 and not R12 in the first place. The potential reasons I’ve considered are:
  • Perhaps AGND goes too high in some mode such that +4V minus AGND becomes less than 2.3V—the min Vin for the ADR3412 (I can’t quite follow the diagram for T1 to see if this is the case)
  • Perhaps the +4V output from the NJU7741F-04 (U13) is too noisy, which might cause the 1.2V reference voltage to fluctuate
There were two other potential solutions I saw, instead of moving that jumper:
  • Add a simple resistive voltage divider to feed perhaps 2/3 the battery voltage into the ADR3412
  • Add a bodge wire to feed the 3.6V VDD output of the NJM2870F-36 (U1) into the ADR3412
A voltage divider would need to be chosen carefully such as to not impede the operation of the meter when using alkaline or NiMH cells. I don’t necessarily see any advantage to using VDD over +4V, although that regulator has an added “noise bypass” capacitor that the +4V regulator lacks, which may reduce noise? Could also replace the +4V regulator with a “better” one if noise is a problem, but that’s perhaps getting excessive.

So I am thinking moving the jumper may be the best choice.

Thoughts? Has anyone else done this mod?

Reference links:
« Last Edit: January 06, 2021, 01:35:23 am by Mr. Wizard »
 

Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #1281 on: January 06, 2021, 04:13:12 am »
Mechanical issue - cracked/broken terminals 2x
#1 occured exactly year down the day of order (#28035) - June 12'th 2019. Therefore still in warranty.
I've reported to Dave but didn't get any response back.

#2 occured just few days ago
The meter is very lightly used. The cables been on/off the terminals max 20x/since new.

Report issue https://www.eevblog.com/product/121gw/ is broken:
[iframe src=”https://docs.google.com/forms/d/e/1FAIpQLSchJyQwmA8YgbfVQsr-JcJmy0k940EpXPiSu–8bBym4pAkRQ/viewform?embedded=true” style=”min-height:200em;”]

And I'm obviously not pleased $200+ meter which I'm generally happy with falls mechanically apart with very light use after 1 year. This didn't happen with $5 meter good 20y old used around the house.
Hope to get resolution of the situation from Dave.

I have no record of any email from your forum account adress.
I can ship you replacement connectors, please email me your adress and number dave AT eevblog.com
 

Offline firewalker

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Re: EEVblog 121GW Multimeter Issues
« Reply #1282 on: January 06, 2021, 09:06:40 am »
Is there any new firmware from UEI?

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Offline drvtech

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Re: EEVblog 121GW Multimeter Issues
« Reply #1283 on: January 07, 2021, 04:51:32 pm »
Input jacks again!
I bought my 121GW less than a year ago and it has one completely broken terminal (common) and one which is cracked (Volts etc). The serial number is 190904517 so it is well outside of the range with the batch problem previously reported. I have emailed the UK company I bought it from (Simon's Electronics) and will report back with their response.
 

Offline dcac

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Re: EEVblog 121GW Multimeter Issues
« Reply #1284 on: January 07, 2021, 09:39:02 pm »
I wanted to find out whether the meter can be used with lithium batteries instead of standard cells or not.
Problem with lithium cells ist the higher voltage. 4 lithium cells have up to 7.7V when they come out of the package. After a short time the voltage goes back to approximate 6.6V and stays a long time at this value.
Problem or not?
I could not find any hint to this question, so I started to explore the schematics.
First it looked good, all internal voltages came from low drop regulators.
+4V, VDD(3.3V) analog supplies and VDD_P  (3.3V) for the 15V booster and the CPU.
So, no problem at all, none of the voltages can go to high.
But wait, what is that?
The voltage reference, ZD1, a ADR3412 reference regulator is connected directly to B+ via R94, a 0 ohm resistor. B+ is the battery voltage. And this is a problem in my opinion. According to the datasheet the input voltage range of the ADR3412 is 2.3V..5.5V, the absolute maximum is 6V.
That means even with alkaline batteries the voltage is above the input range and with new alkaline batteries also above the absolute maximum. With lithium cells it is way off from the allowed input voltage.
Populate R12 instead of R94 will supply the reference with +4V, so no problems in this configuration. But R94 is populated, not only in the schematics. I have checked this in my meter and actually R94 is populated. I will remove R94 and place it in the R12 position.I cannot understand why the reference is connected to B+, that makes no sense for me. Is this really a design flaw or did I overlook something?
I’ve been purging my lab of alkaline batteries, which keep leaking, and replacing them with Energizer lithium cells. The only thing I have that can’t handle lithiums is my 121GW, where its ADR3412 will be fed too high a voltage from fresh lithiums. I figured I might as well move the 0-ohm jumper from R94 to R12 to make the meter lithium-safe, as long as that’s not going to cause any other problems.

Before making the mod, I wanted to check on the forum. I’ve been pondering why the jumper was on R94 and not R12 in the first place. The potential reasons I’ve considered are:
  • Perhaps AGND goes too high in some mode such that +4V minus AGND becomes less than 2.3V—the min Vin for the ADR3412 (I can’t quite follow the diagram for T1 to see if this is the case)
  • Perhaps the +4V output from the NJU7741F-04 (U13) is too noisy, which might cause the 1.2V reference voltage to fluctuate
There were two other potential solutions I saw, instead of moving that jumper:
  • Add a simple resistive voltage divider to feed perhaps 2/3 the battery voltage into the ADR3412
  • Add a bodge wire to feed the 3.6V VDD output of the NJM2870F-36 (U1) into the ADR3412
A voltage divider would need to be chosen carefully such as to not impede the operation of the meter when using alkaline or NiMH cells. I don’t necessarily see any advantage to using VDD over +4V, although that regulator has an added “noise bypass” capacitor that the +4V regulator lacks, which may reduce noise? Could also replace the +4V regulator with a “better” one if noise is a problem, but that’s perhaps getting excessive.

So I am thinking moving the jumper may be the best choice.

Thoughts? Has anyone else done this mod?


I haven't done this mod but here's the possible AGND levels from HY3131:



As you can see AGND can be at 1.8V,  1.08V or 0.36V. If I remember correctly it's at 1.8V for all modes except Ohms which is 1.08V and Diode mode that is 0.36V.

One reason I can think of to not supply the ADR3412 reference directly from another regulator would be to avoid injecting noise into AGND via decoupling caps C18 and C62. Also remember it's not just the regulators creating noise - everything they supply power to also comes into the equation.
 
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Offline dcac

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Re: EEVblog 121GW Multimeter Issues
« Reply #1285 on: January 07, 2021, 09:58:51 pm »
With regard to the broken plastic terminals on 121gw. I’m not at all suggesting this explains what’s happening - but here's just a tip. Whenever I have a new set of test leads I usually first insert them a couple of times in an old DMM with all metal terminals. This to take out a little of the initial springiness and also to shave off any small burrs that sometime is present in the plating or even worse in the leaf springs them self.
 
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Offline Mr. Wizard

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Re: EEVblog 121GW Multimeter Issues
« Reply #1286 on: January 07, 2021, 10:58:37 pm »
I wanted to find out whether the meter can be used with lithium batteries instead of standard cells or not.
Problem with lithium cells ist the higher voltage. 4 lithium cells have up to 7.7V when they come out of the package. After a short time the voltage goes back to approximate 6.6V and stays a long time at this value.
Problem or not?
I could not find any hint to this question, so I started to explore the schematics.
First it looked good, all internal voltages came from low drop regulators.
+4V, VDD(3.3V) analog supplies and VDD_P  (3.3V) for the 15V booster and the CPU.
So, no problem at all, none of the voltages can go to high.
But wait, what is that?
The voltage reference, ZD1, a ADR3412 reference regulator is connected directly to B+ via R94, a 0 ohm resistor. B+ is the battery voltage. And this is a problem in my opinion. According to the datasheet the input voltage range of the ADR3412 is 2.3V..5.5V, the absolute maximum is 6V.
That means even with alkaline batteries the voltage is above the input range and with new alkaline batteries also above the absolute maximum. With lithium cells it is way off from the allowed input voltage.
Populate R12 instead of R94 will supply the reference with +4V, so no problems in this configuration. But R94 is populated, not only in the schematics. I have checked this in my meter and actually R94 is populated. I will remove R94 and place it in the R12 position.I cannot understand why the reference is connected to B+, that makes no sense for me. Is this really a design flaw or did I overlook something?
I’ve been purging my lab of alkaline batteries, which keep leaking, and replacing them with Energizer lithium cells. The only thing I have that can’t handle lithiums is my 121GW, where its ADR3412 will be fed too high a voltage from fresh lithiums. I figured I might as well move the 0-ohm jumper from R94 to R12 to make the meter lithium-safe, as long as that’s not going to cause any other problems.

Before making the mod, I wanted to check on the forum. I’ve been pondering why the jumper was on R94 and not R12 in the first place. The potential reasons I’ve considered are:
  • Perhaps AGND goes too high in some mode such that +4V minus AGND becomes less than 2.3V—the min Vin for the ADR3412 (I can’t quite follow the diagram for T1 to see if this is the case)
  • Perhaps the +4V output from the NJU7741F-04 (U13) is too noisy, which might cause the 1.2V reference voltage to fluctuate
There were two other potential solutions I saw, instead of moving that jumper:
  • Add a simple resistive voltage divider to feed perhaps 2/3 the battery voltage into the ADR3412
  • Add a bodge wire to feed the 3.6V VDD output of the NJM2870F-36 (U1) into the ADR3412
A voltage divider would need to be chosen carefully such as to not impede the operation of the meter when using alkaline or NiMH cells. I don’t necessarily see any advantage to using VDD over +4V, although that regulator has an added “noise bypass” capacitor that the +4V regulator lacks, which may reduce noise? Could also replace the +4V regulator with a “better” one if noise is a problem, but that’s perhaps getting excessive.

So I am thinking moving the jumper may be the best choice.

Thoughts? Has anyone else done this mod?


I haven't done this mod but here's the possible AGND levels from HY3131:



As you can see AGND can be at 1.8V,  1.08V or 0.36V. If I remember correctly it's at 1.8V for all modes except Ohms which is 1.08V and Diode mode that is 0.36V.

One reason I can think of to not supply the ADR3412 reference directly from another regulator would be to avoid injecting noise into AGND via decoupling caps C18 and C62. Also remember it's not just the regulators creating noise - everything they supply power to also comes into the equation.
Thanks, that’s exactly the info I needed. It looks like the mod won’t work. With 4V supplying the ADR3412, 4V minus 1.8V gives 2.2V, which is under the 2.3V minimum of the ADR3412.

Adding a dedicated 5V regulator just for this is also no good, since that would preclude using 4 x 1.2V NiMH cells. Would need something like a TPS7A24 (datasheet: https://www.ti.com/lit/ds/symlink/tps7a24.pdf) low-dropout voltage regulator outputting perhaps 4.2V (requiring a 4.36V or higher input voltage, considering its max VDO).

I suppose I could design a little PCB for that and patch it in, in place of R94. The next time I place a component order, I’ll add one of those.
 

Offline J-R

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Re: EEVblog 121GW Multimeter Issues
« Reply #1287 on: January 07, 2021, 11:21:03 pm »
UEi was quoted in the other thread stating that their jacks are slightly smaller in diameter.  Also, their test leads are not the lantern style, so with those two factors there is far less stress on the jack.  My 121GW came with the UEi leads and they slide in buttery smooth.  The Brymen leads require a lot more force and make snapping sounds especially if removed with a twisting motion.  I'll be sticking with the UEi leads.
 

Offline Mr. Wizard

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Re: EEVblog 121GW Multimeter Issues
« Reply #1288 on: January 08, 2021, 07:36:44 am »
I wanted to find out whether the meter can be used with lithium batteries instead of standard cells or not.
Problem with lithium cells ist the higher voltage. 4 lithium cells have up to 7.7V when they come out of the package. After a short time the voltage goes back to approximate 6.6V and stays a long time at this value.
Problem or not?
I could not find any hint to this question, so I started to explore the schematics.
First it looked good, all internal voltages came from low drop regulators.
+4V, VDD(3.3V) analog supplies and VDD_P  (3.3V) for the 15V booster and the CPU.
So, no problem at all, none of the voltages can go to high.
But wait, what is that?
The voltage reference, ZD1, a ADR3412 reference regulator is connected directly to B+ via R94, a 0 ohm resistor. B+ is the battery voltage. And this is a problem in my opinion. According to the datasheet the input voltage range of the ADR3412 is 2.3V..5.5V, the absolute maximum is 6V.
That means even with alkaline batteries the voltage is above the input range and with new alkaline batteries also above the absolute maximum. With lithium cells it is way off from the allowed input voltage.
Populate R12 instead of R94 will supply the reference with +4V, so no problems in this configuration. But R94 is populated, not only in the schematics. I have checked this in my meter and actually R94 is populated. I will remove R94 and place it in the R12 position.I cannot understand why the reference is connected to B+, that makes no sense for me. Is this really a design flaw or did I overlook something?
I’ve been purging my lab of alkaline batteries, which keep leaking, and replacing them with Energizer lithium cells. The only thing I have that can’t handle lithiums is my 121GW, where its ADR3412 will be fed too high a voltage from fresh lithiums. I figured I might as well move the 0-ohm jumper from R94 to R12 to make the meter lithium-safe, as long as that’s not going to cause any other problems.

Before making the mod, I wanted to check on the forum. I’ve been pondering why the jumper was on R94 and not R12 in the first place. The potential reasons I’ve considered are:
  • Perhaps AGND goes too high in some mode such that +4V minus AGND becomes less than 2.3V—the min Vin for the ADR3412 (I can’t quite follow the diagram for T1 to see if this is the case)
  • Perhaps the +4V output from the NJU7741F-04 (U13) is too noisy, which might cause the 1.2V reference voltage to fluctuate
There were two other potential solutions I saw, instead of moving that jumper:
  • Add a simple resistive voltage divider to feed perhaps 2/3 the battery voltage into the ADR3412
  • Add a bodge wire to feed the 3.6V VDD output of the NJM2870F-36 (U1) into the ADR3412
A voltage divider would need to be chosen carefully such as to not impede the operation of the meter when using alkaline or NiMH cells. I don’t necessarily see any advantage to using VDD over +4V, although that regulator has an added “noise bypass” capacitor that the +4V regulator lacks, which may reduce noise? Could also replace the +4V regulator with a “better” one if noise is a problem, but that’s perhaps getting excessive.

So I am thinking moving the jumper may be the best choice.

Thoughts? Has anyone else done this mod?


I haven't done this mod but here's the possible AGND levels from HY3131:



As you can see AGND can be at 1.8V,  1.08V or 0.36V. If I remember correctly it's at 1.8V for all modes except Ohms which is 1.08V and Diode mode that is 0.36V.

One reason I can think of to not supply the ADR3412 reference directly from another regulator would be to avoid injecting noise into AGND via decoupling caps C18 and C62. Also remember it's not just the regulators creating noise - everything they supply power to also comes into the equation.
I am now thinking I may just remove R94, take a $0.10 78L33 (3.3V through-hole voltage regulator) from my parts bin, connect AGND to its GND, B+ to its VIN and have its VOUT go into the ADR3412. That seems simple enough. I might solder a 0.1 to 1 μF SMD capacitor across its VIN and GND pins, but that may not even be necessary. The trickiest part will probably be finding suitably-thin wire to make the connections.
« Last Edit: January 08, 2021, 07:39:05 am by Mr. Wizard »
 

Offline dcac

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Re: EEVblog 121GW Multimeter Issues
« Reply #1289 on: January 08, 2021, 12:06:16 pm »
I’m not really planing for this mod my self - but I would opt for a regulator with as low quiescent current as possible. A regular 78L would dump a few (4-5?) mA into AGND - that perhaps can handle that - I've no idea. But it will probably also add to the overall current consumption in the APO state of the DMM.

ADR3412 is specified at 70uA (max) quiescent current - so something closer to that perhaps.

« Last Edit: January 08, 2021, 12:07:53 pm by dcac »
 
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Offline Mr. Wizard

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Re: EEVblog 121GW Multimeter Issues
« Reply #1290 on: January 08, 2021, 03:59:04 pm »
I’m not really planing for this mod my self - but I would opt for a regulator with as low quiescent current as possible. A regular 78L would dump a few (4-5?) mA into AGND - that perhaps can handle that - I've no idea. But it will probably also add to the overall current consumption in the APO state of the DMM.

ADR3412 is specified at 70uA (max) quiescent current - so something closer to that perhaps.
That’s a good point. I can’t seem to find from the HY3131 datasheet just how much current AGND can handle. So I should match it better to the ADR3412.  As far as APO, I suppose it depends on whether the firmware sets AGND to floating or not when entering the APO state. It should, but it may not.
 

Offline dcac

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Re: EEVblog 121GW Multimeter Issues
« Reply #1291 on: January 08, 2021, 04:51:31 pm »
In APO state 121gw only seems to kill the 3.6V (U1, NJM2870) so HY3131 gets no VDD. The firmware doesn’t seem to change AGND before killing the power so it stays at its level depending on mode selected. Question is also then what impedance AGND will have with no VDD present.

But anyway, thinking it through - an extra regulator will of course increase the overall power consumption of the DMM - so low quiescent current is a must to not degrade battery life too much.
 

Offline Mr. Wizard

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Re: EEVblog 121GW Multimeter Issues
« Reply #1292 on: January 08, 2021, 06:51:49 pm »
Good point. This means that the TPS7A24 regulator (datasheet: https://www.ti.com/lit/ds/symlink/tps7a24.pdf) that I was considering originally might fit the bill very well. I could tie its enable line to the 3.6V line, so that in APO mode it would draw less than 650 nA. If I set its voltage right, I could use B- rather than AGND for its GND so as to add no more load on AGND.

Honestly, the enable line of the ADR3412 should probably go to the 3.6V line, too, since it appears that currently it stays enabled even in APO, but I am not looking to make overall improvements to the meter—just allow the use of Lithium batteries while not making anything worse. :)
 

Offline curiousmuch

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Re: EEVblog 121GW Multimeter Issues
« Reply #1293 on: January 11, 2021, 05:36:04 pm »
The mA/A range reports 0.8033 mA when the leads are shorted when 5 digits are displayed.
If I hit range and 4 digits are displayed it shows 0.000mA.

Is this a known issue? Is there a list of issues I can check / review. 55 pages is quite a bit.

Thanks! :)

EDIT: Firmware v2.04.
« Last Edit: January 11, 2021, 08:15:56 pm by curiousmuch »
 

Online giosif

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Re: EEVblog 121GW Multimeter Issues
« Reply #1294 on: January 12, 2021, 09:02:39 am »
I've just tried and no such problem on mine (also running v2.04).

For your meter is the problem with mA/A in DC or AC mode?
If in AC mode, if you wait long enough with the probes shorted, does the reading eventually count down to 0?
 

Offline sequoia

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Re: EEVblog 121GW Multimeter Issues
« Reply #1295 on: January 12, 2021, 08:22:54 pm »
I wanted to find out whether the meter can be used with lithium batteries instead of standard cells or not.
Problem with lithium cells ist the higher voltage. 4 lithium cells have up to 7.7V when they come out of the package. After a short time the voltage goes back to approximate 6.6V and stays a long time at this value.
Problem or not?
I’ve been purging my lab of alkaline batteries, which keep leaking, and replacing them with Energizer lithium cells. The only thing I have that can’t handle lithiums is my 121GW, where its ADR3412 will be fed too high a voltage from fresh lithiums. I figured I might as well move the 0-ohm jumper from R94 to R12 to make the meter lithium-safe, as long as that’s not going to cause any other problems.

Seem like a 'trend' with EEVblog multimeters, can't handle lithium AA/AAA batteries.... (or does the new one finally handle them properly?)

Has anyone noticed any real issue using (Energizer) Lithium AA batteries in 121GW?   I've been using them since the unit was new, and haven't noticed any problems....

 

Offline Mr. Wizard

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Re: EEVblog 121GW Multimeter Issues
« Reply #1296 on: January 12, 2021, 10:54:25 pm »
Seem like a 'trend' with EEVblog multimeters, can't handle lithium AA/AAA batteries.... (or does the new one finally handle them properly?)

In the BM786 thread, Dave said it can handle them:

Does it work well with rechargeable AAA batteries?
+1 , and also Lithium cells ? As these have tad higher voltage.

Yes, confirmed ok by Brymen.

I have my EEVblog BM786 running with Lithiums; so far so good but I’ve only had it a couple days and haven’t really measured anything. Didn’t immediately burst into flames, though. 😃
 

Offline Mr. Wizard

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Re: EEVblog 121GW Multimeter Issues
« Reply #1297 on: January 12, 2021, 10:59:41 pm »
Has the PCB layout for the 121GW been published anywhere? I am designing a PCB mod board for it to allow the use of lithium batteries, much as Dave demonstrated in this video, with a tiny voltage regulator and a few other components. I can measure the locations of everything myself with a caliper, but if the PCB layout is available it would save me some work.
 

Offline curiousmuch

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Re: EEVblog 121GW Multimeter Issues
« Reply #1298 on: January 13, 2021, 07:03:16 pm »
Quote
I've just tried and no such problem on mine (also running v2.04).

For your meter is the problem with mA/A in DC or AC mode?
If in AC mode, if you wait long enough with the probes shorted, does the reading eventually count down to 0?

Thanks for the quick reply.  mA/A range only in DC. It only shows this when the probe is inserted into the mAuA Jack and on the 5 digit mA range.
AC mode shows a couple hundred uA but I can see it decreasing. DC mode shows 0.8028 - 0.8033 mA constantly. I can rel it out, but it's kinda of a bummer / annoying.

I've had this meter for about a year and I just noticed it. It's likely out of warranty. It feels like a calibration issue? Has anyone one else seen anything similar. I might review the cal process to see if there is a way to cal only this range possibly.
 

Offline J-R

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  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #1299 on: January 13, 2021, 10:51:41 pm »
Calibration is great on the 121GW because you can back it up to a file on the microSD card and restore it if you make a mistake.  Or copy it to your computer for safekeeping.  You can calibrate each function and range individually.
 


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