Author Topic: EEVblog 121GW Multimeter Issues  (Read 252920 times)

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Offline Bugsyson

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Re: EEVblog 121GW Multimeter Issues
« Reply #275 on: June 18, 2018, 04:06:19 am »
What mode should I try and calibrate? Meter reads correct in all ranges and amp jack position except in "A" jack and in 500mA range which it auto ranges to, but reads the same when manually ranged.
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #276 on: June 18, 2018, 04:54:01 am »
Yes can manual range in both cases, every time you cycle a plug into the jack it goes into auto range.

It still displays 50 mA in both cases?
I suspect at some point your full scale range calibration for that range was calibrated while open circuit. Is this possible?

Have definitely not been in the cal mode, and it really thinks there is 50 extra mA, but only when plugged into the Amp Jack, readings are all good when using the mA/uA jack.

Thats super weird but the solution seems it could be offset error calibration. I suspect somehow this did get calibrated incorrectly.
If you have something to verify the reading after this then you can try zero the offset calibration setting. The steps are in the user manual. Make sure you are in the bad range, very important.
 

Offline Bugsyson

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Re: EEVblog 121GW Multimeter Issues
« Reply #277 on: June 18, 2018, 05:07:01 am »
So what range is the bad one? The 50mA or 500mA, or should I just try and cal both, best I have is an 20 year old fluke 87 ( been calibrated every year) and a 87v never cal'd. Should be alright eh...
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #278 on: June 18, 2018, 05:14:15 am »
So what range is the bad one? The 50mA or 500mA, or should I just try and cal both, best I have is an 20 year old fluke 87 ( been calibrated every year) and a 87v never cal'd. Should be alright eh...

500mA? Thats the one with the error right (getting worried)?
Only calibrate Offset.
 

Offline IanB

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Re: EEVblog 121GW Multimeter Issues
« Reply #279 on: June 18, 2018, 08:22:33 am »
There seems to be a problem with auto-ranging up from the 5 mA range to the 50 mA range. The meter seems to get confused and cannot lock into the reading.

Could you attempt the same test without the burden voltage measurement?
This is because when burden voltage measurement is switched on the multimeter alternates between voltage and current, this might be reseting the auto-ranging.

Yes, without the burden voltage turned on the meter jumps smoothly between the two ranges.
I'm not an EE--what am I doing here?
 

Offline Bugsyson

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Re: EEVblog 121GW Multimeter Issues
« Reply #280 on: June 18, 2018, 10:58:39 pm »
So what range is the bad one? The 50mA or 500mA, or should I just try and cal both, best I have is an 20 year old fluke 87 ( been calibrated every year) and a 87v never cal'd. Should be alright eh...

500mA? Thats the one with the error right (getting worried)?
Only calibrate Offset.

Left it all night and day, came home from work to do the cal and it was working?? Did the 500mA cal anyway, no noticable change in readings. Noticed I could not select 50mA range when in the calibration mode ( no leads inserted) and the same when operating normally, manual range cycles 500mA, 5A and 1000A, it's not until I insert a lead into the mA/uA jack that it will cycle through the 5mA and 50mA ranges, seems right. Still very weird it was out and reading exactly 50.00mA high, I'll let you know if it does it again. Thanks for your help and suggestions everyone.
 

Offline iainwhite

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Re: EEVblog 121GW Multimeter Issues
« Reply #281 on: June 20, 2018, 01:48:24 pm »
Still waiting for my missing 121Gw yellow shim.     5 weeks now.
 

Offline qmif

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Re: EEVblog 121GW Multimeter Issues
« Reply #282 on: June 20, 2018, 02:32:07 pm »
Hi Dave,

Today, I was very glad to receive the 121GW multimeter, but when I opened it, I found some welding troubles.
Although the functions are well tested and the accuracy is perfect, I still have some concerns.

The attached picture shows the problem I found. It looks like something is wrong with SMT process.

Please let me know if the components are not lost, I only need to welding them.
 

Online exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #283 on: June 20, 2018, 04:01:41 pm »
It looks like there is a solder bridge on AD8436.
 

Offline IanJ

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Re: EEVblog 121GW Multimeter Issues
« Reply #284 on: June 20, 2018, 05:20:21 pm »
Also, U3 pin 6 shorted to pin 7....?
Ian Johnston
www.ianjohnston.com
Manufacturer of the PDVS2 & PDVS2mini
 

Online Gyro

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Re: EEVblog 121GW Multimeter Issues
« Reply #285 on: June 20, 2018, 05:59:07 pm »
Did those burns on the casing and L? come from careless hand soldering of J2?
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Online ChunkyPastaSauce

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Re: EEVblog 121GW Multimeter Issues
« Reply #286 on: June 20, 2018, 08:19:31 pm »
It looks like there is a solder bridge on AD8436.
It's probably fine as the schematic shows the two pins shorted; bridging ok in another spot https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-issues/msg1408213/#msg1408213

Also, U3 pin 6 shorted to pin 7....?
Does look kinda iffy

The attached picture shows the problem I found. It looks like something is wrong with SMT process.
Please let me know if the components are not lost, I only need to welding them.
Nothing is missing from what I can tell; unpopulated locations seems to be same as mine
« Last Edit: June 21, 2018, 04:17:40 am by ChunkyPastaSauce »
 

Offline baoshi

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Re: EEVblog 121GW Multimeter Issues
« Reply #287 on: June 23, 2018, 07:16:13 am »
Not sure if anyone encountered this or I just unlucky.
I found my meter reading for voltage rather unstable for some time until today I find it is actually the probe problem.

The black probe jumps around 40-500kohm and after playing for a while it is completely open circuit now.




The probes came with the meter is really nice and I can’t find a replacement source for it. Any tips how can I get this fixed?
 

Offline iainwhite

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Re: EEVblog 121GW Multimeter Issues
« Reply #288 on: June 23, 2018, 11:15:42 am »
For info:  the probes are made by Brymen and they are available on eBay, although you should be able to get yours replaced for free if they are defective.
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #289 on: June 24, 2018, 10:42:26 pm »
Not sure if anyone encountered this or I just unlucky.
I found my meter reading for voltage rather unstable for some time until today I find it is actually the probe problem.

The black probe jumps around 40-500kohm and after playing for a while it is completely open circuit now.




The probes came with the meter is really nice and I can’t find a replacement source for it. Any tips how can I get this fixed?

Please PM me your Kickstarter backer number and email address and I'll organise a replacement.
 

Offline darik

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Re: EEVblog 121GW Multimeter Issues
« Reply #290 on: June 28, 2018, 04:32:17 pm »
Mine does this with v 1.22 (and did it with 1.17 and 1.21). When set to Ohms almost every time I short the probes it will display a random reading in the MOhm range for about a second then it will start autoranging and giving me accurate readings.

It's just cosmetic but I really don't like it, because for a moment it sure looks like it thinks it's giving me an accurate reading.

Do they all do this?

So 95 % of the time the random numbers come up instead of blanking the display while changing ranges. It only occurs on the top M Ohm range and will blank as soon as the auto ranging starts.
Do others see this effect on theirs with firmware version 1.07. ?.

Yes, I see the same thing with 1.07.  When the probes are applied to a resistor the screen blanks for a moment, then shows a random bad value and pauses for a second or two with no sign that it is still working to find the correct value, then it blanks again briefly before showing the correct value with relatively rapid updates to the lest significant digits.
 

Offline IanB

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Re: EEVblog 121GW Multimeter Issues
« Reply #291 on: June 28, 2018, 04:38:09 pm »
Mine does this with v 1.22 (and did it with 1.17 and 1.21). When set to Ohms almost every time I short the probes it will display a random reading in the MOhm range for about a second then it will start autoranging and giving me accurate readings.

It's just cosmetic but I really don't like it, because for a moment it sure looks like it thinks it's giving me an accurate reading.

Do they all do this?


Yes, mine does this. I have been debating whether to log this as a formal issue. I think I may do so.
I'm not an EE--what am I doing here?
 

Offline darik

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Re: EEVblog 121GW Multimeter Issues
« Reply #292 on: June 28, 2018, 09:11:22 pm »
Mine does this with v 1.22 (and did it with 1.17 and 1.21). When set to Ohms almost every time I short the probes it will display a random reading in the MOhm range for about a second then it will start autoranging and giving me accurate readings.

It's just cosmetic but I really don't like it, because for a moment it sure looks like it thinks it's giving me an accurate reading.

Do they all do this?


Yes, mine does this. I have been debating whether to log this as a formal issue. I think I may do so.


I think it's related to the fact that the update frequency is much slower in the 50 MOhm range. If the timing is such that it picks up a reading in that range as the connection is being made it hangs on it and delays the autoranging by the 50 MOhm update interval.
« Last Edit: June 28, 2018, 09:15:40 pm by darik »
 

Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #293 on: June 28, 2018, 11:20:34 pm »
Mine does this with v 1.22 (and did it with 1.17 and 1.21). When set to Ohms almost every time I short the probes it will display a random reading in the MOhm range for about a second then it will start autoranging and giving me accurate readings.

It's just cosmetic but I really don't like it, because for a moment it sure looks like it thinks it's giving me an accurate reading.

Do they all do this?

Yes, mine does this. I have been debating whether to log this as a formal issue. I think I may do so.

Mine with v1.22 only does this sometimes, mostly it's straight to ohms range.
I think if I tap the probes slower or with less force then it happens more, but I'd have to do controlled tests to really see that.
Are you touching the probes with your fingers?
 

Offline darik

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Re: EEVblog 121GW Multimeter Issues
« Reply #294 on: June 28, 2018, 11:41:02 pm »
Mine with v1.22 only does this sometimes, mostly it's straight to ohms range.
I think if I tap the probes slower or with less force then it happens more, but I'd have to do controlled tests to really see that.
Are you touching the probes with your fingers?

I think it happens less often if I tap harder but it hard to tell. I've been very conscious to keep my fingers off the probes. I think it's also pretty important that the meter is stabilized on OFL with a full bar graph before making the connection in order for it to happen.
 

Offline IanB

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Re: EEVblog 121GW Multimeter Issues
« Reply #295 on: June 29, 2018, 12:27:05 am »
Mine with v1.22 only does this sometimes, mostly it's straight to ohms range.
I think if I tap the probes slower or with less force then it happens more, but I'd have to do controlled tests to really see that.
Are you touching the probes with your fingers?

No, not touching the probes with my fingers.

It happens with auto-ranging turned on, measuring a low value resistor ~100 ohms. What happens is when I touch the probe to the resistor lead the display flashes up some 10's of MΩ first, then it goes blank while ranging, then comes back with the right resistance.

A similar thing happens in reverse when I disconnect the test lead. It again shows some 10's of MΩ on the display, then goes blank, then shows OL.

It seems to me that the auto-range feature is trying to be "too quick" to latch on. It sees a momentary contact resistance, and without waiting for it to stabilize, puts it on the display.

I can avoid this happening if I am really quick touching and removing the probe, but it takes an effort to be quick enough.

This is particularly noticeable if using the auto-hold feature. It will latch onto the MΩ value instead of the expected value. In my estimation, auto-hold with resistance is only useful if you manually set the expected range first.

I can maybe make a video of this later, when I get home from work.
I'm not an EE--what am I doing here?
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #296 on: June 29, 2018, 12:30:29 am »
Mine still does this most times , no touching the the probe tips with fingers either !. Its largely cosmetic but I think it would have a more polished look without that random reading showing.
Just blank display briefly at the start of the auto range sequence.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline iainwhite

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Re: EEVblog 121GW Multimeter Issues
« Reply #297 on: June 29, 2018, 02:07:52 am »
Dave & David,
I got my replacement shim & knob today!  Thanks for sending these.    :-+
 

Offline Yannik

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Re: EEVblog 121GW Multimeter Issues
« Reply #298 on: July 04, 2018, 08:26:17 pm »
I have still not received the shim.

I emailed dave, david and susan multiple times about this, yet never got a reply back.

I'm pretty disappointed how this is being handled by dave..
 

Online exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #299 on: July 04, 2018, 10:44:08 pm »
Same experience with emails.

BTW, has anyone tried Low Z measurements? Can somebody check for me if it works for voltages below, say, 5V? It doesn't work for me even on latest firmware (but I think I destroyed calibration data, so can be my bad if it's fixed). It would be great to have a list of bugs somewhere to see what's fixed and what is not.
 


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