[volt-nuts] Homebrew DVM

Fred pa4tim at gmail.com
Wed Nov 16 00:20:50 UTC 2011

The ADC I am gonna use is the LTC2400. A friend who is a digit-nut made
the pcb and will make the software for me.

About the dual slope experiment. I could look better as it is. The
arduino died before I could do more tests but first results amazed me.
Remember it was just breadboard, no Vref (just resistive divider from
Vcc and, I do not dare to say, but the measurement pictures were taken
after I blew up my last 4066, so I used optocouplers to switch and
strange enough that went very well. 

The drift you see in the measurements is more because the powersupply I
measured the voltage from, is not realy stable. Noise I do not know.

The experiment was after a discussion on a Dutch forum. There was some
talk about multimeters and ADCs and the a member who works at ST as an
EE told the top meters used dual slope about how easy it is to make a
dual slope ADC. He told us to just try it on a breadboard and gave some
tips. A few of us including me started experimenting with it and I was
trilled it was so easy to get it working like it did. Was fun too. I'm
now reading a lot of literature and your interesting discussions to
learn more before I build my meter using the LTC2400. So thanks for all
the valuable information. As a beginner I appreciate it very much.


Andreas Jahn schreef op di 15-11-2011 om 23:19 [+0100]:
> Hello Fred,
> I asked for the 26 bit (24 bit usable) ADC.
> Do you really get this (noiseless) resolution with a simple dual slope ADC?
> With best regards
> Andreas
> >
> > http://www.pa4tim.nl/?p=2482 there you see the schematic and some pictures 
> > ( the top one is from the circuit that, i was told, turned out to be a VF 
> > converter)
> >
> > Fred PA4TIM
> >
> >> I am looking now for a converter with less noise.
> >> So what ADC are You using?
> >>
> >>>
> >>> Now I have a 26 bit ( 24 bit usable) ADC waiting to be used interfaced 
> >>> to the arduino, I am making/experimenting with some Vrefs and have parts 
> >>> for a compound chopper based on a LT1052. But the realisation will be up 
> >>> in the future, first gathering more knowledge about percision and micro 
> >>> volt techniques.
> >>>
> >>> Fred PA4TIM
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