[time-nuts] pointers to information on ways to collect data, 5335, etc.

[Magnus Danielson]

Hi Jim,

On 03/09/2012 10:27 PM, Jim Lux wrote:
> I've got a student intern (Undergrad Senior) who's doing a project for
> me where he's trying to synchronize (and syntonize) two 1 pps ticks,
> generated from different oscillators using some modules in an FPGA.
> One oscillator is a run of the mill 66 MHz clock oscillator the other is
> a 49.x MHz TCXO. (and, of course, because he's working in a breadboard,
> I can swap in a signal generator for either.. I've got a stack of 3325Bs
> and 8663s, etc.)
>
> The objective is to get two signals that are 1 pps (or 10 pps) ticks
> (each derived from a different oscillator) that align
>
> I'm looking for info to point him to on evaluating the performance of
> his implementation.
>
> I've got a HP 5335 (which works quite nicely with a Prologix and John
> Miles's tools... thanks John!). I've got oscilloscopes. I've got access
> to more exotic stuff if need be (although, since my intern budget is
> skinny, stuff I happen to have in the lab, like my uncalibrated 5335, is
> better)

For the application, the 5335 will be more than adequate.

> I also have a bunch of Wenzel 10 MHz OCXOs sitting around (although for
> this, why not use one of the instrument's internal oscillator and
> distribute it around)
>
> I do have a hydrogen maser derived reference in the lab, but I'm more
> interested in him measuring the two oscillators against each other.
> (that is, measuring the performance of the TCXO, by itself, isn't
> particularly interesting)
>
>
> What he needs is some suggestions on things that he can measure that
> would be meaningful figures of merit for the application.

He should measure:

- Lock-in transient
- Lock-in time/time-constant
- Lock-in overshot
- Estimate control loop bandwidth and Q-value/resonance

He should then also have a "lock" detector, possibly several lock levels 
and illustrate them in the transient waveform.

Then, he should measure the lock-in deviation pattern and measure bias 
and RMS noise. Maybe even do a nice ADEV/TDEV set of plots. MTIE plots 
is always nice as well.

Showing good control of model parameters and actual performance remains 
a good thing. It is usually good to attempt to improve things.

A good exercise is trying to figure out ways to get quick and dead safe 
lock-in while also get good in-lock performance. :)

I strongly recommend having a digital scope in parallel with the counter.

> He's not doing a PhD dissertation, though.. And he has to be done before
> the end of the spring semester. No million second Allan Deviation
> measurements.

Should be a good project for him. Keep me posted on the progress.

Cheers,
Magnus