> 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?

First, check out the 16F628.  It is a newer replacement for the 16F84 that
does more and costs less.

The 16F628 only has a comparator, no A/D.  Thermocouple signals are slow, so
you could use a low pass filtered PWM output as one input to a comparator
and the thermocouple as the other.  The 628 has two analog comparators built
in, so that's how many thermocouples it can handle without external
multiplexing or additional external comparators.

> 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?

The thermocoulple will measure the temperature difference between the two
ends of the two-conductor wire formed by the two wires of the dissimilar
metals.  One end of this two-conductor wire is "shorted", and is the
temperature probe end.  The other end of the two-conductor wire eventually
transitions to two conductors of the same metal, usually copper.  The
temperature of that junction needs to be controlled or known.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics