On Thu, 05 Nov 2009 11:12:46 -0600, John Fields
wrote:

On Thu, 5 Nov 2009 16:20:21 -0000, "ian field"
wrote:


"John Fields" wrote in message
. ..
On Wed, 4 Nov 2009 22:09:04 -0000, "ian field"
wrote:


"John Fields" wrote in message
m...
On Wed, 4 Nov 2009 13:17:24 -0000, "ian field"
wrote:

What would be the minimalist circuit blocks for a frequency domain
sample
and hold?

What I envisage is the sampling triggered by a tone that exceeds a
pre-set
threshold and continues to generate a copy of the tone until reset.

---
I'm confused...

What do you mean by 'sampling' and what do you mean by 'threshold'?

Sample a frequency - the analogy with "sample and hold" is once the
frequency is recognised, something like a VCO continues to reproduce the
frequency until a reset.

Threshold is when a tone exceeds a set amplitude it triggers the sample
action, so as to prevent background sounds confusing the circuit.

---
OK, that's doable.

Next, do you need the copy to be a sine wave, like the original, or can
it be a square wave

Also, what kind of frequency/phase accuracy are you looking for with
regard to the difference between the source and the copy?

What else can you tell us? Voltages, power, etc, etc.

You know, the details the devil's in.

Its for feeding a digital frequency counter, so it can be converted to a
square wave at any point in the process.

The objective is for a frequency range equal to all the keys on a piano, it
needs to be fairly accurate.

---
There may be a much simpler way to solve whatever problem you need the
gadget for.

What's your application?

JF

Sounds like piano tuning... he hits a key, and wants "sustain" (while
he counts it ??)

He'd be better off starting a high speed counter when both amplitude
and "zero-crossing" conditions are and measure period. Then invert to
get frequency.

...Jim Thompson
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