In this work we describe an experimental setup to measure vapor pressures and evaporation coefficients with the Knudsen method at elevated temperatures (1100 K to 1800 K) with a quartz crystal microbalance and an electron beam evaporator. Details of the experimental setup are presented, and the theoretical basis to calculate the vapor pressure data from measured quantities is given. The results for the well-known vapor pressure of copper demonstrate the proper operation of the setup. For SiO, new results are presented. We confirmed the value for the SiO evaporation coefficient but derived a lower vapor pressure compared to existing literature data.