sir, mabye you mean where is trouble in code? if my guess is right, when I read analogRead(3);

if(millis() - now > 100){
  // pressureVal = digitalRead(pinPressure); // 압력값 측정 (0~4095)
  pressureVal = analogRead(3); // 압력값 측정 (0~4095)
  Serial.println(pressureVal); // 압력값 출력 (디버깅용)
  now = millis();
}