Testing the quality of a spot weld consists of determining the temp. of the weld directly after welding (T0t0) and then after a certain time (T1t1) interval by measuring the thermoelectric voltage induced between the parts or electrodes. The voltages are used to determine the temps. from a previously drawn graph and when the value of T0(t1-t0)/T0-T1 is below a threshold value previously determined the weld is considered insufficiently strong (a cold shot).
