Re: thermocouple to pc connection by serial port?

On 22/12/2005 the venerable onehappymadman@xxxxxxxxx etched in runes:

>
> Sven Wilhelmsson wrote:
> > onehappymadman@xxxxxxxxx wrote:
> > >
> >
> > > 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?
> >
> > Yes, probably. But read the specs on DC offset and stability for
> > the PWM circuit carefully, as a thermocouple normally has a rather
> > low DC output voltage.
> > /SvenW
>
> Say, where could I find the specs on the max. peak voltage that the
> Microphone Input on a soundcard can take, without distorting and of
> course without damaging it?
>
> I tried google for microphone specs, but found instead all sorts of
> audio-related data instead of peak-to-peak max voltage. Is the max
> typically 1V? 5V?
>
> I don't have an oscilloscope, otherwise I'd just measure the outputs
> from my CD player headphone jack...
>
> Thanks,
>
> Mike

Why not use a MAX6675 thermocouple interface with cold-junction
compensation? It has an SPI compatible interface which can very easily
be connected to an AVR mega8 with a serial port.

--
John B
.

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