Temperature sensors based on the temperature memory effect in shape memory alloys to check minor over-heating

Abstract

In many occasions, such as in cold chain logistics, upon delivered to the customers, a cost-effective technique to check if any individual items (rather than a whole big box of them) have ever been slightly overheated is ideal for quality control. In this paper, we propose a possible method not only to check such an over-heating event in individual items, but also to reveal the highest temperature using NiTi shape memory alloy (SMA) via one single differential scanning calorimeter test. Three different types of temperature memory effect are investigated and the most applicable one, i.e., with good estimation of the actual over-heating temperature, is identified. The detailed implementation procedure for real practice is presented and the strategy to improve the accuracy is discussed. It is shown that in terms of checking the actual over heating temperature, a precision of within ±0.5°C is achievable in both tested NiTi SMAs.