Author Topic: have ever you seen multimeter back light change the last counts on the display?  (Read 4398 times)

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Offline modz786Topic starter

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The culprit is a newly acquired OWON XDM1241.

Anytime the backlight intensity is turned up from zero the last digits change by around 3 to 5 counts.

Has anyone experienced the same with a factory stock multimeter of any brand?

I  emailed OWON and in two days responded with an exploration from the teckies and I wait to see.

Perhaps I might be offered a firmware upgrade we shall see.
« Last Edit: December 16, 2022, 06:56:35 am by modz786 »
 

Offline AVGresponding

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No, I haven't!

I wonder if the vref is just the regulated supply for the meter logic ICs and dips a little when you load it up with the backlight?
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Offline Brumby

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That's not something I have encountered either - but I agree with AVG's suggestion that the voltage reference might not be as stable as you would hope.  The other possibility being the higher current in the backlight circuit is being coupled to the measuring circuitry by some means - which, if it were the case, would suggest either a poor physical layout, a faulty component or a component not fitted properly.

I am curious as to whether this phenomenon is better/worse at different ranges and is/isn't proportional to the measured quantity.
 
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Offline Kanbus

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Not the same but similar. My OWON B41T+ adds an extra degree when backlight turns on while measuring temperature. Turn on bluetooth and you go up one more degree. So logging temperature with any confidence is out of the question.

The com terminal on the POS also broke recently.
With great power comes great smell
 
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Offline modz786Topic starter

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Now I have this quirk I will do some testing across all ranges over the week end.
I agree the display power supply is taken NOT from its own regulator circuit more like an after thought but without the obvious wire soldered across the board.
I bought the OWON out of curiosity and was on sale price with 0.05% DC and it takes up no real estate unlike my ancient Fluke 45

OWON replied to me in two days and I wait for engineers assessment.
 

Offline AVGresponding

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Now I have this quirk I will do some testing across all ranges over the week end.
I agree the display power supply is taken NOT from its own regulator circuit more like an after thought but without the obvious wire soldered across the board.
I bought the OWON out of curiosity and was on sale price with 0.05% DC and it takes up no real estate unlike my ancient Fluke 45

OWON replied to me in two days and I wait for engineers assessment.

It might be possible to mod it to improve the situation, in this case. I'd bet even without the backlight issues it can't match the F45 for accuracy though...
nuqDaq yuch Dapol?
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Offline modz786Topic starter

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well I thought the same but a 5V reference (AD584JH) using masterprobes measured with Fluke 8846A reads 5.00024

10v is Fluke 8854A 9.99933, OWON is 9.999 Fluke 45 9.9999
2.5v is Fluke 8846A 2.49674, OWON is 2.497 Fluke 45 2.4966

OWON 5.0001
Fluke 45 5.0000

Fluke 45 I havent calibrated and its feathers aparts with 8846A and the OWON is not bad on DC accuracy BUT its accuracy is best with the BackLite OFF and the screen is very readable its really nice but Im still an old school fan for VFDs

 

Offline modz786Topic starter

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reply from owon...so if it falls within 5 counts it makes no difference what other factors affect the readings but they dont understand or refuse to acknowledge its hardly user trustworthy if you have to ask yourself what is the true reading when display light is on or off and the brightness options are 0, 25,50,75 100%
« Last Edit: December 16, 2022, 08:37:13 am by modz786 »
 

Offline marks2c

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XDM1241-U SN: 22400093

Not seeing this effect on either ac or DC ranges, incl mV, when powered from the supplied 18650 batteries.
 
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Offline modz786Topic starter

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interesting your sn is newer my sn 22190668.
My version firmware is V3.3.1

is yours the same?

I brought in June 2022 from Banggood and after sales are a waste of time it tooks weeks for a reply that asked for a video, that was two weeks back.
« Last Edit: December 17, 2022, 06:50:26 am by modz786 »
 

Offline AVGresponding

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reply from owon...so if it falls within 5 counts it makes no difference

 :palm:

 |O
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Offline modz786Topic starter

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checked ohms, ACV, Temp no issues but another quirk of OWON is reverse the test lead polarity with back light on of off it gives different readings. Not even my various uni-t meters or other china brands I try and the Fluke45 just laughs at this carry on
 

Offline marks2c

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V3.8.0. Does not even vary by one count on mV DC.

It is a tier-3 meter with a BA of 0.05%, DC-UPS that can be powered from 5V, all this while taking measurements and being controlled by SCPI. All for US$135 incl rapid international delivery. All in all: pretty darn good.

That said, the meter should meet spec. My suspicion is that OWON addressed the issue (firmware and/or H/W fixes).

« Last Edit: December 19, 2022, 02:46:54 am by marks2c »
 

Offline modz786Topic starter

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yep snap good specs especially battery powered and or 5v USB C.
I suspect a newer firmware is needed and have asked OWON to send me this.
I gave up with Banggood and went to OWON direct.
 

Offline marks2c

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Did you have any luck with Owon direct?
 

Offline modz786Topic starter

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After this email they ignore my requests.

So if a fault causes drift but its within their specs then its normal.

So what do I do ? wait for this drift to pass outside specs then they do something? LOL

I wouldn't buy OWON again after the poor customer service.

A firmware upgrade sent via email may have helped but they dont respond.

« Last Edit: January 24, 2023, 08:03:50 am by modz786 »
 

Offline modz786Topic starter

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its the same count drift in any DC range. Resistance range not affected

I also tested with the unit on charge and no change.
« Last Edit: January 24, 2023, 07:58:42 am by modz786 »
 

Offline AVGresponding

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Have you had a look inside it, to see whether it might be possible to mod it to take the BL supply from the pre-reg part of the psu?
nuqDaq yuch Dapol?
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Offline modz786Topic starter

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A consideration for Easter break but I shouldn't be moding a under warranty meter and OWON completely no responsive to further requests for just a simple update for the firmware.

Thanks
 

Offline py-bb

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Yeah when the battery is low. This can't be helped. There will be a voltage it needs to work, below that it's not fair. The backlight uses a bit of power batteries drop voltage as you load them (the curve varies from battery to battery)


So seriously don't hold it against it

I fucking love my Dialog PL280N which has a button and the backlight stays on until you press it again - I can leave it somewhere and watch it


There should be an icon on the display which indicates low battery.
 

Offline Gerhard_dk4xp

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I heard about a Tektronix sampling plug in where the trigger LED
affected sampling time or amplitude. A few ps are much there.

Gerhard
 

Offline ironcurtain

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Did you ever manage to get any firmware update files from OWON?

I have a newer revision but have not had the time (yet) to test if the drift is still present there. It makes sense that a low battery condition might trigger this. Does it happen if you leave it connected to a 5V DC source?
"If you are going to fail, at least do so spectacularly."

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Offline modz786Topic starter

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Hi OWON is a waste of space, morons and talking with someone that does a lot testing of equipment told me his experience for tech support for donated and paid for out of his pocket that this is the case for not wanting to help they try to always blame operator error and refuse to possible software bugs or hardware issues.

I dont remember if the problem persists with power connected for charging and to what degree if not the same when testing but I will try when I unpack as I moved recently.

If anyone has received firmware from OWON perhaps they could share it on the forum Thanks
 
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Offline ironcurtain

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I will try to put some time aside to test mine, and look around for any firmware files.
"If you are going to fail, at least do so spectacularly."

Kurtz: [intercepted radio message] I watched a snail crawl along the edge of a straight razor. That's my dream; that's my nightmare. Crawling, slithering, along the edge of a straight razor... and surviving. -- Apocalypse Now (1979)
 

Offline modz786Topic starter

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OK unboxed just now and cold start we read following

5v source (5.00024) in calibration fluke 8840 reading

OWON in Auto V

ambient room temp 25 Celsius

Mid speed

4.9995 backlight off

4.9992 backlight 100%

4.9993 backlight 50%


after warm up 30 mins

4.9990 backlight  0ff

4.9987 backlight 100%

4.9988 backlight 50%

with and without 5v charge results same.

Resistance ranges not affected by backlight
 


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