A simple technique has been devised to reduce the number of lead wires needed to connect an array of thermocouples to the instruments (e.g., voltmeters) used to read their output voltages. Because thermocouple wires are usually made of expensive metal alloys, reducing the number of lead wires can effect a considerable reduction in the cost of such an array. Reducing the number of wires also reduces the number of terminals and the amount of space needed to accommodate the wires.

Heretofore, it has been standard practice to use a separate lead wire to connect to each side of each thermocouple. In other words, it has been standard practice to use 2N lead wires to connect to N thermocouples.

A Single Common Wire for the negative sides of N thermocouples is formed into a branched wire. The thermocouples are formed at the tips of the branches.
The essence of the present technique is to use one common, grounded wire for the negative sides of all the thermocouples in the array and to connect the positive side of each thermocouple, in the customary manner, to the positive terminal of the instrument used to read its output. Fabrication of the array begins with twisting of the single negative-side wire to form branches for thermocouples (see figure). The root of each twisted branch is then heated to shunt the twist, thereby reforming the twisted and untwisted portions of the wire into a continuous piece of branched wire. Next, thermocouples are formed by joining one end of each positive lead wire to the tip of one of the twisted branches and the other end to one of the output terminals. If the number of thermocouples formed in this way is N, then there are only N + 1 lead wires (the one common negative wire and N positive wires) and an equal number of terminals.

This work was done by Jon C. Goldsby of Glenn Research Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Computers/Electronics category.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Commercial Technology Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-17181.

Topics:
Alloys Connectors and terminals Electrical systems Electronics & Computers Fabrication Joining Manufacturing processes Metals
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This article first appeared in the August, 2003 issue of NASA Tech Briefs Magazine (Vol. 27 No. 8).

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