So you are using digital noise filtering?
1. Are you using FFT and cutting the upper frequencies? (much computing power required for this for real-time.)
2. OR... are you just chopping off some of the lower bits (noise) of the A-to-D output? (300 Hz not required for this and not much computing power required for this.)
Just curious.
If you already have a link to info describing your noise filtering technique that would be easier for you to answer with that.
I haven't spoken with Ralph about this for quite a while, however, yes the C-Meter software does use low pass FFT filters. When the C-Meter was in devleopment it was not possible to adequately represent the input resistance (which goes from near zero to near infinity) with enough bits to see small reads over the whole range and also simply chop off low order bits.
Also, as I guess you know, the ADC process is inherently noisy. And the first chips produced quite a bit of it. Later ones are much better judging by the software settings I have to use with the two digital meters I've had from Ralph. The latter one also has an analogue, regular needle movement (driven off the digital half of the meter), which smooths pretty well all the noise just by virtue of needle inertia.
I am not convinced that FFT is necessary. I've had quite good results in simulations using simple, multiple, low factor exponential moving averages. Ralph smiles his inscrutable smile when I say this.
Nick
Excuse me programmer guy.... yer right I overlooked something there 
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Found one online store with some in stock as many outlets are sold out right now.
