EEVblog BM235 FW E issue with resistance measurment and auto / manual range - Page 1
Forum section: electronics / testgear

author: Herr R aus B
author_rank: Regular Contributor
timestamp: October 26, 2018, 03:38:30 pm
content: Hi!This thread is related to this older thread on a rather dobious ebay seller, where i purchased one of the older EEVblog DMM with firmware E:https://www.eevblog.com/forum/testgear/eevblog-dmm-reseller-confirmation/msg1211025/#msg1211025Now I discoverd a rather annoying issue with FW E, which I couldn't find any article on the forum - so maybe that's of any interest to who knows whom ;-) To put it short: When measuring in the 10K range I find, that values below 56K are displayed one order of magnitude too high, when auto ranging is selected - so 33K becomes 330K, 47K becomes 470K and so on. So then. when trying manual range selection I find, that in the k-Ohm range the decimal point is not advanced properly - showing .0L -> 0L. -> 0L. - and the issue occurs when being in the assumed 0.L range - which is display as 0L. tho - but disappears when swithing to the oL. range.I thought, this is maybe better shown in a video, hence I uploaded this short clip to YouTube:https://youtu.be/dmhOf0tUwM4So maybe this is of any interest for someone out there having one of the older versions. Would alsobe interesting, if this issue is reproducable :-)I guess I have to bare with this, because of the impossibility of FW upgrades - thanks to the strange ebay seller who shipped the meter despite i cancelled the order and got refunded after the seller immediately claimed not having the DMM in stock and that I would have to wait 2-3 months, I just payed customs and import tax anyway, so I can live with the issue, especially as I also have a later version G DMM, properly bought from Dave over amazon :-)RegardsAxel

author: joeqsmith
author_rank: Super Contributor
timestamp: October 27, 2018, 03:51:56 pm
content: The BM235 I have uses revision D firmware. I tried repeating your test and went so far as to use several other values and was unable to replicate it. It seems like the alignment on your meter may have been wrong for the one range.

author: Herr R aus B
author_rank: Regular Contributor
timestamp: October 27, 2018, 04:11:06 pm
content: Quote from: joeqsmith on October 27, 2018, 03:51:56 pmThanks for the effort :-)I might have to look closer into it - also regarding as well 100K/1M ranges as 100/10/1 ohm ranges... but then, I dont have any clue, how to fix the alignment. On the other hand side FW E might even have bugs, that weren't present in D - at least having been a software developer for a long time and now doing µC stuff I discovered, that fixing one bug can make other bugs show up unexpectedly :-)Is there somene with FW version E to maybe try to replicate the above dexcribed behaviour? :-)RegardsAxel

author: joeqsmith
author_rank: Super Contributor
timestamp: October 27, 2018, 04:41:13 pm
content: Have you tried to contact Brymen to see if they offer this service or if they have any recommendations for anyone in your area?Odd it would get out of the factory like this. Maybe someone along the way attempted a home alignment.

author: commongrounder
author_rank: Frequent Contributor
timestamp: October 28, 2018, 02:43:48 pm
content: I don’t believe it is a calibration or “alignment” issue. It appears to be a bug in the firmware that simply misplaces the decimal point in the 10k range, both auto and manual. If you imagine the decimal point in the correct position on that range, the meter is making accurate measurements (and over-ranging at the proper point in manual mode). Of course, that doesn’t make the problem any less annoying, or instill confidence in the reading.