We want to use TAS2552EVM board to measure the dc resistance of a speaker. The testing signal is a pilot tone sine signal. After amplification the voltage across the speaker is 50mVpeak, and the resistance of the speaker is around 8ohm, thus the power is around 1.5e-4 W.
From the measurement, we found that there exist harmonics of I-sensing signal, while the V-sensing signal seems quite clean.
It is noticed that on page 11 of TAS2552 manual, the THD+N percentage of I-sense for 8ohm load increases greatly to 5% for 0.001W. In our case, the power is even lower, does it mean that the THD+N is even higher?
If we want to calculate the dc resistance accurately, how could we know the THD+N value at 1.5e-4 W?
Many thanks!
