A. method: set a=0~1, this filter result = (1-a) * this sample value +a* the last filter results.

B. advantages: periodic interference with good inhibitory effect, suitable for occasions with higher frequency.

C. disadvantages: phase delay, sensitivity low degree of latency depends on a size cannot eliminate filter more frequently than the sampling frequency one-second interference signals.

E. test code

int Filter_Value; 
int Value; 
  
void setup () {
   Serial.begin (9600); / / initialize the serial communication 
   randomSeed (analogRead (0)); / / random seed 
   Value = 300; 
} 
  
void loop () {
   Filter_Value = Filter (); / / get the filter output value 
   Serial.println (Filter_Value); / / serial output 
   delay (50); 
} 
  
/ / Used to randomly generate a current value of around 300 
int Get_AD () {
   return random (295, 305); 
} 
  
/ / First order lag filter method 
# define FILTER_A 0.01 
int Filter () {
   int NewValue; 
   NewValue = Get_AD (); 
   Value = (int) ((float) NewValue * FILTER_A + (1.0 - FILTER_A) * (float) Value); 
   return Value; 
}