Dmm Yokogawa 732-02 ohm measure issue

[Netmark]

Hi guys,
I have 2 dmm yokogawa 732-02, one of them being battery corrosion. After cleaning, the corrosion dmm measure in ohm range is slow. When you take lead test into resistor the number go higher compare to normal one before come back to precision value. It still precision, but slow measurement  compare to normal one.
I have tried to cleaning main chip and resistor that it use in ohm range and expose it to sun light. After that its measurement become fast as normal one. But after a few day, it slow again @@
Please help me find out problems!
Or any suggestion.
I also want to know more about dmm schematic and its working principles, could you suggest any good book.
Thanks and sorry about my english!

[MathWizard]

With auto-ranging on DMM's, sometimes when oil/dirt from my hands, gets on the probes, the DMM will take longer.

Can you really measure a time difference ? I'd use the same probes, even the same battery, turn on or off auto-ranging, and compare them.

As for books/manuals, look up DMM service manuals, most of the top DMM's from before the 1990/2000's, have nice detailed manuals, with theory of operation, and schematics.

There's lot of old analog volt/ohm/amp meters too, like Heathkit, all their manuals are in a few archives.
Heathkit Schematic and Manual Archive
https://www.vintage-radio.info/heathkit/



Besides the chips getting smaller, I don't think much has changed, and most DMM's work about the same.

Fluke87 DMM
https://xdevs.com/doc/Fluke/83_85_87smeng0500.pdf

[Netmark]

Thanks for your rely,
This is the test of normal one
https://youtu.be/BQF7JXbeKCo?feature=shared
This is the defective one
https://youtu.be/2mgGlNrlJdw?feature=shared
It's easy to feel the different of measure speed
If i try to wait a little, the number will go down, example in test 1 ohm resistor that it will count down to 1.1 but very slow.
I use the same probe. Battery be tested in good condition for all
May be, i need to desolder chip and relevent resistor, then cleaning and soldering again. May be it will resolve the problems, because it is new dmm but storage with battery inside, so the issue come from battery corrosion. Just guess @@