Matthew,

Yep that's definitely possible with the F84A. I'm
working on a similar project (but with analog
acceleration inputs instead of thermocouples). So
here's a suggestion -- get a multi-channel ADC. For my
current project I'm using Microchip's MCP3202 (if I
remember the part name correctly), which has two
separate channels and lets you send 12 bit ADC values
over an SPI serial connection, which is only four
wires -- perfect for the 16F84's PORTA (and an LCD can
go on PORTB -- I'm using a Seiko 1671 16x1, which uses
up 7 of PORTB's bits). I'm sure you can find 4 channel
ADCs or more out there that connect over serial lines
(number of channels=number of thermocouples you can
connect up). I've worked with K-type thermos before,
you'll most likely have to connect it up to an op-amp
based amplifier (you can get instrumentation
amplifiers on a chip, they're really good for those
low voltage levels) then send the amplifier output to
the ADC. As for extending the leads, the voltage
output of the thermocouples is already small, so to
save yourself a lot of headaches you're probably best
off just ordering the length of thermocouple wire you
need. You can get it in pretty much any length (just
make sure that the ends have already been welded, and
you're not getting two rolls of unconnected wire). If
you solder stuff onto the end to make a short
thermocouple longer, you're going to throw your
measurements way off. Hope that helps you out...

- T.C.

> Dear all,

> I am (very) new to the world of PIC's but not to the

> general world of electronics.  My question is: how
> many K-Type Thermocouples can I connect to
> a PIC 16F84A?

> I am wanting to use the PIC to display the readouts
> of various temperature probes (all K Type), on one
> single 20x4 LCD screen.  Is this possible with
> this chip or do I need to move up to one with an ADC

> incorporated?

> I am aware that I will need one AD595 for each
K-Type
> thermocouple.  Also,how can I extend the leads of
the
> thermocouples without creating errors in the voltage

> created by the difference of the original 2 metals?

> Thanks for your time,

> Matthew.

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