Hi, I am currently trying to suppress the noise signal from 50Hz and above for the LM35 output pin.
To do this, I connect the output pin to a 2nd order Butterworth low pass filter.
The current issue I faced is that the output signal after going through the low pass filter had its noise signal suppressed(dropped from -90dB to -100dB) BUT it would leave behind 2 peaks(-90dB & -95dB) at approximately 400Hz and 800Hz. May I know how to eliminate the two peaks?
Original LM35 output signal:
LM35 output signal after passing through low pass filter:
2nd order Butterworth low pass filter design:
R1 = R2 = 6.6k ohm; C1 = 47nF; C2 = 22nF
2nd order Butterworth low pass filter bode plot diagram:
To do this, I connect the output pin to a 2nd order Butterworth low pass filter.
The current issue I faced is that the output signal after going through the low pass filter had its noise signal suppressed(dropped from -90dB to -100dB) BUT it would leave behind 2 peaks(-90dB & -95dB) at approximately 400Hz and 800Hz. May I know how to eliminate the two peaks?
Original LM35 output signal:
LM35 output signal after passing through low pass filter:
2nd order Butterworth low pass filter design:
R1 = R2 = 6.6k ohm; C1 = 47nF; C2 = 22nF
2nd order Butterworth low pass filter bode plot diagram: