Source Of Uncertainty?

jhaible jhaible at
Tue Nov 23 23:01:57 CET 1999

> Can someone explain to me what features the BUchla Source of Uncertainty
> has.  Is there anything that makes it special in the way of random voltage
> sources?

Where are these schematics when you need them (;->). So this is from
memory, the part that I found most interesting:

Noise is fed into a triangle / square oscillator in a way that it produces
a certain random frequency variation. (You can also interpret the maths
of this configuaration as a 1st order PLL, btw.) The Triangle output
of the noisy oscillator is then run thru the Sample&Hold. This must result
in something very close to uniform distibution of the S&H output (as
opposed to the bell shaped distribution of other S&H's that run from
white noise.)
So far, this was simplified. The S&H is not directly fed by the
noisy triangle wave, but there is a variable mix (like a panpot) between
the noisy triangle, and the S&H output voltage fed into the S&H input.
With this potentiometer you can set the correlation of the S&H, as you
choose which part of the last step, and which part of the random
signal will be used for the next sample.


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