hello friends,
I have the following problem:
The internal multimeter in my SONY-Tek305DMM (this is a fully seperated board with own DCDC to be full isolated) have a problem when testing OHMs.
AC, DC is allready working.
Description: When testing R, it star like counting, after a longer time it stop at the right resistance.
100k: longer time to be right
10k: short time to be right
zero Ohms: longer time.
Videos to watch that directly,
attention large files around 14MB:testing a 100k.
http://www.wellenkino.de/305/v1.avi picture from the stop:
testing a 10k.
http://www.wellenkino.de/305/v2.avitesting with shorted cables:
http://www.wellenkino.de/305/v3.avithe service manual is here:
http://www.wellenkino.de/305DMM/305DMM.pdf (!! 25MB)
I think the current source with the Fet and the OP will make that problem. Good tips are needet.
greetings
Martin