The temperature sensor built in most modern hard disks may give improper results. The difference between the measured and the actual temperature can be 7-9 Celsius degress or even more.
To fix this problem, it is possible (and recommended) to measure the actual temperature of the hard disk by using an external infrared thermometer or a front panel with temperature sensor and set the difference between the measured temperature and the temperature displayed by Hard Disk Sentinel (reported by the drive itself) as temperature offset. This is called calibration.
After the real temperature has measured (by the thermometer or other external temperature sensor), the offset can be calculated by subtracting the value reported by the software from the measured value. This offset can be positive (the software reports smaller temperature than the real) or negative (the software reports higher temperature than the real).
This offset can be specified on the S.M.A.R.T. page of the hard disk, after selecting attribute #194 (hard disk temperature) and using the + / - buttons (by clicking on the number between the icons, the offset value can be entered directly in Celsius units).
Hard Disk Sentinel will automatically increase (or decrease) all hard disk reported temperatures by the configured offset value. This way the correct (real) temperature will be displayed and used in all cases (for example, when checking hard disk temperature against a threshold and when saving reports etc.)
It is recommended to perform the temperature calibration on all installed hard disks if possible. Same type of hard disks may require different temperature offsets.
Note: if the calibration is not possible (the computer chassis cannot be opened), an estimated offset value can be determined by checking the first displayed temperature immediately after starting the computer and comparing the value with the environment (room, office) temperature. At this time, the CPU, video card or other components are not too warm and they do not affect the temperature of the hard disk. Of course this is true only if the computer had enough time to cool down to the environment temperature (it was not powered off for at least 8 hours).
For example, if the hard disk temperature is displayed as 17 Celsius degrees (immediately after starting the computer) and the room temperature is 22 Celsius degrees, +5 can be configured as offset value (because the hard disk cannot be cooler than its temperature). This offset is better than nothing but of course an external thermometer is needed to determine the proper temperature offset value.
Note: the temperature offset should be specified in Celsius units, regardless of the selected temperature unit (Celsius or Fahrenheit).
Note: the unregistered version automatically resets all offset values to 0 when the user restarts Hard Disk Sentinel.