Increasing ADC resolution At this moment I am using oversampling to increase my analogread resolution.
This in combination with increasing the frequency of the ADC.
Is someone able to take a look at it?

#define FASTADC 1
// defines for setting and clearing register bits
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &amp;= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif

int value[100];   // variable to store the value coming from the sensor
int i=0;

void setup() 
{
  Serial.begin(9600) ;
 int start ;
 int i ;

#if FASTADC
 // set prescale to 16 (1MHz)
 sbi(ADCSRA,ADPS2) ;
 cbi(ADCSRA,ADPS1) ;
 cbi(ADCSRA,ADPS0) ;
#endif
}

void loop() 
  { 
  for (i=0;i&lt;100;i++)
  {
   value[i]=Read12bit(0);
  } 
  for (i=0;i&lt;100;i++)
  {
   Serial.println(value[i]);
  } 
  Serial.println();//Some blanks between values
  Serial.println();
  delay(5000);

}


int Read12bit(uint8_t pin){
      int Result = 0;
      analogRead(pin);                      //Switch ADC
      for(int i = 0;i &lt; 16; i++) {          //Read 16 times
        Result = Result + analogRead(pin);  //Sum results 
      }
      Result = (int)Result/4;               //Divide by 4 for 12 bit value
      return(Result);
    }


At this moment the resolution of this oversampled analogread is 12-bits. With a little calculation the time to read will take 0,208milliseconds. If I want to increase my resolution more i.e. 13-bit. This will take the measurement 0,832 milliseconds. This seems rather big, so my question is can I do this in another way?

EDIT
Why?
I am trying to position multiple linear actuator using multiple arduino's connected via CAN-bus (the arduino's will not communicate with eachother unless an error occures) THe positioning has to be precise (&lt;0.1mm on a 30 cm rod).

Why is 12 or 13 bit accuracy and/or resolution needed? 

12 is probably enough. But I just like to find out the boundaries of the equipment :)

What real world processes are being monitored that 0.012% perbit step sizes are not swallowed in the noise of reality? 

Probably none 13-bit resolution is probably too high for my application anyways.

Other reason why I like a higher resolution
First couple of voltages I cannot use. My sensor gives a 4 to 20mA signal which i convert with resistor to ground.
Yes, you can use an external ADC chip. You can get SPI and I2C ΣΔ ADC chips at 16-bit and higher quite easily.

I often use the MCP3553 which allows 60sps at 22-bit.