The Sensors tab in GPU-Z is useful if you are tracking the GPU load or memory usage. The real-time graphs are updated at a frequency of once per second.
The current value of sensor data is useful, but what is more useful is the minimum, maximum and average. There are 2 ways to view these: Click on the dropdown arrow beside each sensor name and make your pick. Or click on the sensor value (number) and it will cycle through these data on each click.
Finally, if you want a log file of the sensor values, click on Log to file. You can selectively remove certain sensors from showing up in the log by clicking their dropdown arrow and disabling Log to file.
Tried with: GPU-Z 0.5.1