Thermometers with temperature resolutions of equal or better than 1 mK typically make use of platinum wire temperature sensors such as the PT100. Alternating current techniques to read out these fairly low dynamic temperature sensors are complex and expensive and act slowly. This work shows that it is possible to build up a thermometer with even higher resolution up to 75 mu K, capable of delivering a data-rate of up to ten readouts per second by means of negative temperature coefficient sensors. We selected the measurement of two binary solid liquid phase diagrams (biphenyl/naphthalene and biphenyl/benzophenone) to check the presented equipment.