[time-nuts] Distribution amps and slew rate

Bob Camp lists at rtty.us
Sat Nov 3 19:05:11 EDT 2012


Hi

If you have a sine wave, it gets into everything. You can identify it and take it out of your data.

If you have a broad band uber-fast high level pules, it gets into everything. Identifying it's impact and taking it out of the data - not so easy.

That may sound a bit crazy. I've actually worked in a place that went over to a square wave based system. It lasted for about a day. Got into all sorts of things, total nightmare.

Bob

On Nov 3, 2012, at 5:44 PM, David Hooke <dhooke at gmail.com> wrote:

> 
> 
> 
> Folks,
> 
> Given that slew rate is so critical, why do we distribute sine waves and perform the zero-crossing detection at every target instrument?
> 
> david
> 
>> Trigger jitter is the noise at the trigger point. it's a combination of thermal noise and the slew-rate at the trigger points. It is often that trigger jitter is dominated by slew-rate, but there is also internal sources of trigger jitter. The slope dependent trigger jitter follows the formula:
>> 
>> t_jitter = v_noise / s_slew
>> 
>> t_jitter is the trigger jitter (s)
>> v_noise is the noise power (V)
>> s_slew is the slew rate (V/s)
>> 
>> When the time-span of a measurement is long, long-term stability comes in as well as systematic drifts. Also, systematic noise such as hum also becomes important.
>> 
>> To see how much you depend on slew-rate limitation, you can reduce the amplitude, and as this reduces the slew-rate you can separate the slew-rate dependent jitter from the intrinsic jitter of the input. It also helps you to identify if you need to work on the slew-rate limit rather than anything else.
>> 
> 
> 
> 
> 
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