  There is a growing demand for experiments on calorimetric and thermal
transport measurements at ultra-low temperatures below 1 mK and high magnetic
fields up to 16 T. Particularly, milligram-sized solid samples are of great
interest. We present the development of scalable thermometers based on quartz
tuning fork resonators immersed in liquid 3He and adapt hydrodynamic models to
provide an improved description of temperature dependence in the high viscosity
regime between 1 and 10 mK. We demonstrate successful thermometer operation and
discuss the feasibility of fast and compact thermal probes suitable for small
samples.
