unstable current readings 0n electronic load

i try , explain best can, have project need alter current using pwm (battery tester), have preset value of 3amps adjust sensor value , when battery voltage fall need decrease sensor value maintain 3amps having little issue
if try code, current readings start increase until 3amps reached readings  become unstable jumping 2.75amps 3.2amps , sensor value fluctuates between 232-235

code: [select]


if ((!cutoff_voltage_reached) && (vresults1<= current_draw)){
// decrease duty cycle compensate smaller load
sensorvalue--;
if (sensorvalue < 195){ //set minimum current value 2.50amps
sensorvalue = 195;  //set minimum current value
}
}
  else if ((!cutoff_voltage_reached) && (vresults1>=current_draw))
// increase duty cycle compensate larger load
sensorvalue++;
if (sensorvalue >255){ //set maximum current value 3.0amps
sensorvalue = 255; //set maximum current value 
}   
  pwmwrite(9,sensorvalue);

to combat seems work current increase's 3amps reading stable , sensor value not fluctuate holds @ 232,if current passes 3amps sensor
value not increase above, think because of delta =abs(last_current - vresults1);

code: [select]


 delta =abs(last_current - vresults1);  // calculate absolute value of difference between previous , current light value
  if (delta<vresults1){ // adjust duty if current falls
  if ((!cutoff_voltage_reached) && (vresults1<= current_draw))//{
// decrease duty cycle compensate smaller load
sensorvalue--;
if (sensorvalue < 195){ //set minimum current value
sensorvalue = 195;  //set minimum current value
}
}
  else if ((!cutoff_voltage_reached) && (vresults1>=current_draw))
// increase duty cycle compensate larger load
sensorvalue++;
if (sensorvalue >255){ //set maximum current value
sensorvalue = 255; //set maximum current value 
}   
  pwmwrite(9,sensorvalue);
  last_current = vresults1;

how write code obtain smooth readings , if current increases or decreases pwm(sensor_value) if increase/decrease input voltage(battery voltage),
i need adjust current if falls above or below preset value if input voltage increased or decreased happens on period of time, i've @ p.i.d don't suited using pwm

why not use basic lm317 current shunt....simple , accurate.

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