Thermocouple alloys — identify the exception: Which of the following commonly used thermocouple materials does not contain nickel in its composition?

Introduction / Context:
Industrial temperature measurement often uses thermocouples made from specific metal alloys. Knowing the principal constituents of these alloys helps with selection, compatibility, and troubleshooting. This question tests recognition of nickel-containing thermocouple materials and asks you to spot the exception—if any—among standard names used in plants and labs.

Given Data / Assumptions:

• Alumel, Chromel, and Constantan are standard thermocouple or lead wire alloys.
• The task is to determine which listed material lacks nickel in its composition.
• We consider conventional compositions used in K-, J-, and T-type systems.

Concept / Approach:
Recall the compositions: Chromel is primarily nickel with chromium (typical K-type positive leg). Alumel is a nickel-based alloy containing aluminum (plus manganese/silicon) and serves as the negative leg for K-type. Constantan is a copper–nickel alloy (about 55% Cu and 45% Ni) widely used with copper (T-type) or iron (J-type) in some configurations. Since all three contain nickel, none of them is nickel-free.

Step-by-Step Solution:

Verification / Alternative check:
Thermocouple reference tables list K-type as Chromel–Alumel (both Ni-based), and Constantan’s shorthand (Cu–Ni) confirms nickel content. This cross-check eliminates ambiguity.

Why Other Options Are Wrong:

Common Pitfalls:
Misremembering Constantan as copper-only. It is consistently a copper–nickel alloy, hence does include nickel.

Final Answer:
None of these