[time-nuts] Sub Pico Second Phase logger

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Dec 15 21:34:34 UTC 2008


Joseph M Gwinn wrote:
> Bruce,
>
>
> time-nuts-bounces at febo.com wrote on 12/11/2008 08:36:47 PM:
>
>   
>> Joe
>>
>> Attached is noise spectrum (1kHz and below) of AP192 with nothing
>> connected to inputs.
>> Sampling rate 96KSPS.
>> Frequency bin equivalent noise bandwidth ~ 3Hz.
>> Noise has similar spectrum to flicker noise with a noise corner of
>> around 300Hz or so.
>>     
>
> The noise floor ain't so bad, -130 dB (dBm? dbV?) at maybe 10 Hz, even if 
> it's 20 dB worse than at 1 KHz.
>
> Has anyone measured the Allan Deviation?
>
> Joe
>
>
>   
Joe

Noise plot is with respect to full scale (4Vrms).
I need to build a noise source to check the absolute level.
Will use the amplified Johnson noise of a 150K resistor.

By Allan deviation do you mean calculate it from the sequential 96KSPS
ADC output samples?

I can do this, but since the dominant noise source is white the Allan
deviation will scale with the measurement bandwidth.

Bruce




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