HIGH PASS FILTER (HPF)
HPF allows only high frequencies (above cut off frequency) and attenuates low frequencies (below cut off frequency). The electronic HPF (passive) is implemented by placing an input voltage across a series combination of a capacitor (C) and resistance (R). The voltage across the resistor treated as an output. The product of R and C value is the time constant (T) of the filter. Time constant is inversely proportional with cut off frequency at which the output power is half of input power.
The mathematical expression between time constant and cut off frequency is
Cut off frequency = 1/2πT = 1/2πRC.
In our project HPF is designed using 0.1 micro farad capacitor and 100 kilo ohm resistor. Time constant of HPF is 0.01 sec. and cut off frequency is 15.92 Hz.