Linear Variable Differential Transformer in Harsh Environments - Analysis of Temperature Drifts for Different Plunger Materials

Linear variable differential transformers (LVDTs) are precise linear position sensors capable of measuring position over a wide range. The selection of the plunger material, whether magnetic or non-magnetic, becomes relevant in environments characterized by high temperatures and temperature variations. Especially for sensors with larger measurement ranges, the sensitivity with respect to temperature increases. In this work we present an LVDT design for large displacements which offers a significantly reduced sensitivity with respect to the temperature. Our design uses a plunger made from solid copper. The proposed sensor design has improved linearity and lower temperature drift with respect to existing designs e.g. sensors with ferrite based plungers. From simulations and experiments we demonstrate a temperature stability of -28.5 to 25.5 \,\mu \mathrm{m}\mathrm{/}\mathrm{K}, which is comparable to other LVDT designs, which use further temperature compensation techniques. We further study the benefit of our design even for non-uniform heat distributions.