Abstract: A probe assembly for planar or chip-type sensors and heaters, which includes a probe housing having a tip end and a feed-through end, and a sensor or heater element within the housing which includes electrode pads and has a bottom surface that is in thermal contact with the probe tip. The assembly includes a means of applying a first compressive force to the element such that thermal contact between its bottom surface and the probe tip is maintained. Electrical lead wires (ELWs) within the housing provide respective conductive paths between the electrode pads and the feed-through end, each ELW including at least one spring portion which provides a second compressive force that acts to maintain physical and electrical contact between the ELW and its respective electrode pad. The assembly is arranged such that the first compressive force is independent of the second compressive force.