Products > Test Equipment
FLUKE 189 DC reading problem [with video]
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joeqsmith:

--- Quote from: CDaniel on July 15, 2019, 08:16:44 pm ---So pretty much everything is bad and in the low side ... the schematic for this meters I don't think it's available but you should try to find and measure the precision voltage reference and power supplies for the analog part ,  before condemning the ASIC chip itself ...
The input protection can't explain the current measurement being off ...

--- End quote ---

After seeing the second video, it behaves different from what I first thought.  With the data you posted,  I concur  with the above post in that probing the reference would be the first step.  I wasn't able to find a schematic for it but it shouldn't be too difficult to trace this area out.   Just takes time.  Maybe just have a look around that REF43 under a microscope.   Someone had posted some decent pictures here:


https://www.eevblog.com/forum/testgear/fluke-187-189-or-87-iv-schematic/
kamcm:

--- Quote from: joeqsmith on July 15, 2019, 09:13:36 pm ---
--- Quote from: CDaniel on July 15, 2019, 08:16:44 pm ---So pretty much everything is bad and in the low side ... the schematic for this meters I don't think it's available but you should try to find and measure the precision voltage reference and power supplies for the analog part ,  before condemning the ASIC chip itself ...
The input protection can't explain the current measurement being off ...

--- End quote ---

After seeing the second video, it behaves different from what I first thought.  With the data you posted,  I concur  with the above post in that probing the reference would be the first step.  I wasn't able to find a schematic for it but it shouldn't be too difficult to trace this area out.   Just takes time.  Maybe just have a look around that REF43 under a microscope.   Someone had posted some decent pictures here:


https://www.eevblog.com/forum/testgear/fluke-187-189-or-87-iv-schematic/

--- End quote ---




I had check out the REF43 area and cannot find anything wrong under a microscope.



I have also test how much current my Fluke 189 draw from the battery. Here is the result.













With the Fluke 189 power off, I still able to measure 55.9M between COM and V socket under 1000V testing.   :bullshit:
Anyway, I just order some IPA from RS and I am going to clean the board completely with IPA.



joeqsmith:
I doubt cleaning the board will do anything for you.  The meter's case looks in very good condition, at least it doesn't appear to have been abused too bad.  I would get another meter and start probing that reference.  Obviously, you will need a decent meter to do this.   Data sheets are on-line for it. 
joeqsmith:
For a reference, the attached graph is looking at the current draw of a working Fluke 189 under various conditions.   Full disclosure,  this data was collected with a home made meter I have been playing around with but I don't see anything strange with yours.    If you want more details about this testing, goto the link in my signature.  There is a TOC on the first page. 

Interesting enough, I am playing with this home made source meter now and am using a low cost Brymen BM869s to detect the trends.   It has a 500,000 count mode which has worked out fairly well for this.   
kamcm:
I just cleaned the whole board (both side) with IPA  8)





But the problem remain the same.  |O



I also noted that when the reading is not correct, if I press the range button to get the reading under manual range, the reading will go crazy out of range. :bullshit:

Which components are likely failed ? Is it the resistance network? how can I test it out ?

Please advice,

Thanks!




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