[time-nuts] Lead acid battery noise levels

[ed breya]

NiCd batteries should have the lowest noise for their size due to low 
resistance, but if you look at ever-lower frequency, the Hg should be 
superior since it has the most stable voltage with time and 
temperature. Drift (including self-discharge) and temperature 
variation response can appear as very low frequency noise independent 
of the other noise sources and operating conditions. Hg batteries are 
so stable that they were commonly used as voltage references or to 
power small circuits without any additional regulation needed.

Ed


 >Mike Feher wrote:

A long time ago, when I was concerned about a phase noise issue, I found an
old NBS article. It was on measuring phase noise and included a schematic of
an ultra-low noise amplifier. In that amplifier they used Mercury batteries.
I also glanced at the referenced article, stating NiCad is the lowest noise,
and, NiCads were available for a long time, yet they used Mercury.  Regards
- Mike
 >