Method and apparatus for inferring a temperature

A heat-conducting element having known length D is disposed at a first end in a first region having a first temperature T1 to be inferred. The second end of the element is disposed in a second region having a measureable second temperature T2 different from the first temperature. The element is well-insulated between the first and second regions. Heat flows along the element from the higher temperature region to the lower temperature region, and the temperature of the element at any point along the element is proportional to the temperature difference between the two regions and the distance from either one of the regions. By measuring the second temperature and also a third temperature T3 at a point along the element, and knowing accurately the position Dn of that point with respect to the first and second ends of the element, the first temperature can be inferred by proportionality.