Re: Thermocouple mux 16 ch(4067) + A/D max187

["max" <maxitubo@xxxxxxxxxxx>]

Hi Marc,

Thanks forthe answer.

Yes the AD 595 contain an Alarm circuit that control if thare is a open TC(2
wire open) but isn't necessary to use it.

I tough to switch only the positive laed of TC and connect all 16 negative
lead togheter with the common ground of the circuit ..?ve seen that some
rotary selector for TC switch only 1 wire and the other are connect togheter
to gound. I?ve seen bad?
This can create some error?
My problem is that i dont't know how to control via Parallel port 2 4067
mux.
Yes i'll keep the ad595 and leadsTC at the junction at the same temperature
"Marc F Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> ha scritto nel messaggio
news:9fakp1hk98sqduuil6h5g7eiv1tb1ep608@xxxxxxxxxx
> On 8 Dec 2005 08:22:30 -0800, "maxi" <maxitubo@xxxxxxxxxxx> wrote in
message
> <1134058950.500626.43440@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:
>
> >i'm building a 16 ch nterface for reading 16 TC type K.
> >I want switch the 16 TC only on positive wire and negative in common on
> >ground with 74hc4067.
> >Aftert the mux i place a AD595 and after a max 187 for reaDIN ON
> >PARALLEL PORT on PC.
> >Somebody has already made this?
> >Do you think that is function?
> >Any tips?
> >
> >Ciao,
> >Massimo
>
> Why do you want to "switch the 16 TC only on positive wire" ?
>
> Conventionally one would use a two CD4067/4051's etc or a CD4052 to switch
> _both_ leads of the thermocouples.  Typically this would be followed by an
> amplifier. And one of the inputs would go to a temperature reference to
> provide "ice point" reference.
>
> But the AD595 (which I haven't used) incorporates amplification and ice
> point, so you would seemingly just need to assure that the thermocouple
> leads and the AD595 are at the same temperature but I don't know what the
"
> thermocouple failure alarm" circuitry consists in (that might be a
> complication -- I don't know).
>
> Or did I misunderstand your question?
>
> Marc
> Marc_F_Hult
> www.ECOntrol.org