The High-Temperature Fluid Measuring Cell is a flow-through device that allows measuring the electrical conductivity of highly corrosive aqueous fluids in dependence of pressure and temperature. So far, the facility was used to study geothermal high-temperature reservoirs at temperatures up to 425 °C and fluid pressures up to 350 bar. Beyond the determination of intrinsic fluid properties, the measuring cell is capable to study the effect of fluid–rock interactions at supercritical conditions.