|
From: Joerg H. <in...@jh...> - 2008-10-30 11:00:11
|
Hi, Robert Mayster, 29.10.2008 23:56 : > Hi Joerg, > > thanks a lot for your help - I shorted the resistors one by one like you > described and it looks like there is really a problem with the calibration > circuitry (probably the easiest part of the whole soldering - d'oh!) > I checked my scope - although it isn't too well calibrated i can safely > assume that the calibration signal I get from the board is about 25uV > instead of 250 uV. Factor 10 too low? Have a close look (visually or with a multimeter) at R240! Is it really 100 Ohms or more 10 Ohms? If this is OK a 2nd candidate is R227 and R223 are not 1meg but 10meg. Check this out too! > I will now try to mock a 250uV signal with my function generator to see > whether this works better. A function generator might be problematic if it is mains powered. Regards, Joerg |