Re: thermocouple to pc connection by serial port?


Sven Wilhelmsson wrote:
> mrdarrett@xxxxxxxxx wrote:
> >
> > Oh, gee, thanks. I thought the USB would be hardest... here I thought
> > I could rip apart an old mouse for some hardware...
>
> Yes, maybe. It has got the serial interface hardware already made.
> But I don't know how to connect to it ... roll the ball ?..
>
> >
> > I'll ponder this some more. low-voltage-DC to AC... hmm... would it be
> > easier to have the circuit vary the frequency or the amplitude as the
> > DC voltage changes?
>
> ---
>
> To vary the frequency would be the most accurate, because errors in the
> sound-card could easily be avoided.
> To vary the amplitude would probably be easier. You could chop the small
> sensor signal directly using a HC4066 switch or a mos (or dmos) transistor
> and amplify the AC, thus an accurate DC amplifier is not really needed.
> Calibration is needed, I would think. Use some intermediate chopper
> frequency in the range 200Hz-1kHz. Use a multiple of the net frequency, 50
> or 60 Hz.
>
> /Regards, Sven W


How about pulse-width modulation, insted of conversion to AC? Would it
work to take the DC from the thermocouple, run this through a PWM
circuit, then connect the output of this to the sound card?

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