In this paper a novel compact Spice model of a thermal conductivity detector (TCD) is presented and validated against an extensive experimental characterization and 3D simulations. The TCD used is based on the ultra low power (ULP) technology and it has been electrically characterized with different helium and nitrogen gas flow rates, via a microfluidic experimental setup. Extraction of global electro-thermal parameters, exploited for the development of the Spice model, has been performed by using both 3D electro-thermal FEM simulations made with COMSOL Multyphisics® and experimental measurements. The first result we discuss is the good agreement between 3D FEM simulations of the device, made with COMSOL Multiphysics®, and the experiments, with a maximum error of 2.9% for He flow rate of 9 sccm and around 1.8% for the N2 carrier gas at each considered flow rate. We have demonstrated that …