Re: pVPD Dual Range ADC results

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From: John Mitchell (John.W.Mitchell_at_nasa.gov)
Date: Thu Jan 23 2003 - 12:09:12 EST

Bill,
8 dB is a factor of 6.3 in power (dB = 10 log [P2/P1]), but only 2.5
in amplitude (dB = 20 log [A2/A1]) since power goes as the square of
amplitude. I think you are seeing exactly the right relationship to
within the precision of the attenuators. No problem in adding
attenuation is we need more range. I can also make differential
splitters with the needed ratio.

John

At 3:42 PM -0600 1/22/03, W.J. Llope wrote:
>hello - just some new results from the localmon data...
>
>the correlation between the high and low range
>pVPD ADC values for a given channel is very tight. this
>makes the rationalization of these two scales very easy...
>
>see the attached for (LR_adc-pedestal) in blue and
>(HR_adc-pedestal)/slope in magenta for pvpd ch 0,
>where "slope" is the scale factor extracted extremely
>accurately from fits of HR vs LR in single chs...
>after pedestal subtraction and scaling the HR ADC
>for the attenuation the resulting adc dustributions match
>up very well in shape i'd say....
>
>one puzzle at the moment (at least in my mind) is
>that these scale factors are only a factor of ~2.4, while
>the attenuators in front of the HR ADCs are 8 dB...
>i.e. i would have thought the HR ADCs would be more attenuated
>by more like a factor of 6.... comments?
>
>regards,
> bill

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