Not only digitising scopes, of course.
toggle quoted messageShow quoted text
As an extreme example, the Tek 1502 TDR has a sampling
rate of ~10kS/s, but can display 140ps risetimes since its
front-end bandwidth is >2.5GHz. That's why it is beneficial
to specify both the sampling rate and the front-end bandwidth.
And the first sampling scope I saw used a XY pen plotter
as an output device :)
Note that for digital signals the period/frequency is irrelevant.
All that matters is the transition time, since that's the principal
influence on the "signal integrity".
On 20/06/17 23:53, 'Dennis Tillman' @Dennis_Tillman_W7PF
You are taking Nyquist too literally. If all you had was one chance to
sample a waveform the Nyquist Criteria would apply but if the waveform is
repetitive then you have an infinite amount of time to sample it or to build
up a set of samples. This is like the difference between a waveform that is
a single shot or a waveform that repeats.
These were the early days of digital scopes and many clever schemes were
needed to achieve excellent bandwidth (1GHz to 3Ghz) with the relatively
slow sampling speed available in those days. The 11403A is capable of GHz
bandwidth on several channels as long as you are measuring repetitive
A single shot waveform only gives you one chance to sample it (or one chance
to display it on the CRT of an analog scope). Your eye has to be really fast
to see the entire one shot waveform or to study any part in detail. A
repetitive waveform refreshes the phosphor of the CRT over and over and you
eye has a chance to study any part of it in detail for as long as you like.
Dennis Tillman W7PF
Sent: Tuesday, June 20, 2017 2:00 PM
Subject: [TekScopes] Re: 11403A as bench scope, how useful is it?
The biggest weak spot is the 20MSPS maximum sample rate. The shortrecord length is not so great either.
Is it really that low? Wow.
Using my typical rules of thumb that gives you a good look at square
waves up to about 2MHz (5th harmonic is 10MHz, Nyquist rate -> 20MSPS).
Not great at all. Surely it has some tricks to be better for non