Calibration of Software/Measure activity

[Mitch Bradley]

Ceramic resonators are less expensive than crystals.  Their stability 
and accuracy is not as good as crystals, but is much better than RC 
oscillators.

The waveform that comes from most oscillators is nominally a square 
wave, but when the frequency gets into the tens of megahertz range, it 
usually doesn't look particularly square on an oscilloscope.

In order of cost, from highest to lowest, the usual timing alternatives are:

a) Self-contained crystal oscillator
b) Built-in oscillator circuit stabilized with a crystal
c) Built-in oscillator circuit stabilized with a ceramic resonator
d) Built-in oscillator circuit timed with RC components.



Ian Daniher wrote:
> As work on a USB ADC continues, somewhere along the lines the problem 
> of calibration came up both with regards to the sound card, and the 
> in-development peripheral.
> It was quickly suggested that a crystal oscillator based circuit be 
> used to generate square waves to help calibrate the time scale of the 
> measure activity.
> This might also help calibrate voltages, as well.
> I bounced this suggestion off the ##electronics guys and the 
> conversation went something like this:
> (02:10:12 PM) *DyDisMe:* Crystal oscillators generate square wave 
> pulses, right?
> (02:10:19 PM) SpeedEvil: depends
> (02:10:29 PM) SpeedEvil: you can get them producing anything from 
> squarewave to sine
> (02:10:43 PM) SpeedEvil: to some sort of rectangle poorly specified.
> (02:11:00 PM) *DyDisMe:* I'm attempting to come up with a method of 
> cheap calibration
> (02:11:10 PM) SpeedEvil: For what?
> (02:11:16 PM) *DyDisMe:* the soundcard of the hardware I'm developing 
> for is built with 5% parts.
> (02:11:17 PM) icee: most oscillators you buy put out squarewave though
> (02:11:20 PM) icee: oscillator modules
> (02:11:22 PM) *DyDisMe:* ok
> Anyone have suggestions, questions, comments, etc?
> -- 
> Ian Daniher
> it.daniher at gmail.com <mailto:it.daniher at gmail.com>
> Skype : it.daniher
> irc.freenode.com <http://irc.freenode.com>: DyDisMe
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