[time-nuts] quartz drift rates, linear or log

[jimlux]

On 11/12/16 1:54 PM, Tom Van Baak wrote:
> There were postings recently about OCXO ageing, or drift rates.
>
> I've been testing a batch of TBolts for a couple of months and it provides an interesting set of data from which to make visual answers to recent questions. Here are three plots.
> <snip>
> The plots show that an OCXO doesn't necessarily follow strict rules. In a sense they each have their own personality. So one needs to be very careful about algorithms that assume any sort of constant or consistent behavior.
>
>
> <snip>

I think this is a general rule: when they make precision oscillators 
(USOs) for spacecraft, they make a fairly large batch (a couple dozen) 
to some intermediate level of assembly, and then they run them for a 
while and watch them, and from that, they pick the "good" ones.  (where 
good is somewhat mission dependent).

The good ones go through the rest of the assembly process into the "box 
level" and, then, from those, the "really good" ones are selected.