Re: Question regarding thermocouples and a voltage terminal block

On 13 Dec 2006 09:19:14 -0800, "kd6532" <kd6532@xxxxxxx> wrote:

Interesting. I am wondering, since tc's basically convey the
temperature as the potential difference between the two conductors,
using a different metal at the junction would not alter this potential
that we will be measuring across the copper and the constantan. And
just out of curiousity, using a metal doesn't typically change the pot.
difference does it?

Thanks again,
Kris

John Larkin wrote:
On 13 Dec 2006 08:13:57 -0800, "kd6532" <kd6532@xxxxxxx> wrote:

Right now some peers and myself are designing a pv module testing
system, in which, one of the things we will be testing is temperature.
To do so we will be using four thermocouples on each solar panel, and
we wanted to join the four into a voltage terminal block to reduce the
amount of wires we will be running to our multi tracer. The problem is
we are having trouble finding a terminal block that will establish a
CLEAN connection and allow us to connect the four wires in and have
just one coming out for both the copper and constantan leads. Is their
a better way to approach this? We found one promising terminal block at
Phoenix Conacts that is specifically constructed for thermocouples
composed of copper/constantan, but four leads cannot go into one of the
inputs, and the tech. support basically told us to try another route.
Any suggestions are welcomed, and thanks for your time.

Kris

Are you going to parallel the tc's into one signal pair? If so, *any*
terminal block will work fine. Just find one big enough to squish all
five wires together. Or crimp them into a *** splice, any wires in
either or both ends (3 in one end, two in the other maybe), doesn't
matter.

John


As long as the junctions are isothermal, they can't generate any
potential. As a practical matter, scrunching some number of wires
under a screw, or crimping them into a *** splice, will be
isothermal.

And oh, we like to bottom-post here.

John

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