Hi

You can precisely measure the temperature near the notch area of a sample by the following steps:

1- connecting one edge of a thermocouple (thin) wire to the side of notch area of the sample.  

2-The other edge of  thermocouple wire should be directly connected to a thermometer, i.e., a digitized thermometer, in order to record/read the instantaneous temperature of the sample.  

3-I would connect the edge of the thermocouple wire to the sample by a thin insulator tape.

4-Not only taking an average of recordings, of at least two  tests, on samples with the same conditions, but also the standard of deviation of the average value should be within  a reasonable value ,i.e., +/- 5%, with an error bar of 10%.      

Thank you for your answer. The problem is that you have to remove the thermocouple just before the pendulum crushes.

Dear Kazasidis

You are right as far as removing the thermocouple just before the pendulum crushes.   However, I would  try not to remove the thermocouple before the pendulum crushes, especially if the thermocouple thin wire was connected to  the side of notch area of the sample  in a way not to affect the reading of the impact test, i.e.,  a bit accessed thermocouple thin wire .