jittery response from arduino potentiometer

Changing the value from the arduino to a float will not help you. The arduino sends a value between 0-1023.

Everytime you send a Serial.println() (which you're doing often in your Arduino sketch), you bang the contents of the zl group and send them out, which is not needed.

Not sure what you're doing with the 107 in the [sel] object either. That indicates that every time you send the letter 'k', you bang the zl group also.

Look at the Arduino code and patch below, based on this tutorial : http://www.arduino.cc/en/Tutorial/SerialCallResponseASCII
I assume you're using a mega or similar with more than 6 inputs, but you should get an idea from how to scale it.

Also, if you don't have all your inputs wired up (or grounded), you'll get a lot of noise.

Arduino sketch :

int inByte = 0;         // incoming serial byte

void setup() {
  // start serial port at 9600 bps and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB only
  }
  establishContact();  // send a byte to establish contact until receiver responds
}

void loop() {
  // if we get a valid byte, read analog ins:
  if (Serial.available() > 0) {
    // get incoming byte:
    inByte = Serial.read();

    for (int i = 0; i < 5; i++) {
      Serial.print(analogRead(i));
      Serial.print(",");
      delay(1);
    }
    Serial.println(analogRead(A5));
  }
}

void establishContact() {
  while (Serial.available() 

max patch :