TechTool Pro does not read temperatures as such, by using the temperature probe in the drive. It reads the S.M.A.R.T. data that the drive itself records in its own firmware. On some drives, there is a S.M.A.R.T. attribute that refers to the drive’s temperature.
The program compares the threshold for a particular S.M.A.R.T. attribute, which the drive mechanism maker put in the firmware, to the current value for that attribute, which the drive itself wrote during use. If the current value for a particular attribute is below the threshold for that attribute, a failure is reported when TechTool Pro examines the S.M.A.R.T. data. That is the way all S.M.A.R.T. reporting works. The only differences among programs are which attributes are being read, and how the results are being reported (text report, dialog box, graph, for example).
