Investigates the calibration procedures and signal interpretation methods for 'single normal' and 'single inclined' hot-wire probes as they are used in turbulent flows. In particular the method of yaw calibration has been more closely examined using two different procedures. The results show significantly different yaw correction factors depending on the procedure chosen. A detailed study of the necessary assumptions in the two methods was therefore carried out and physical explanations are given for the discrepancies.