rtd interfacing with arduino

dear sir,
       i using pt100 wheatstone bridge circuit measure change in resistance. input voltage wheatstone bridge circuit  5v arduino. output voltage @ 33 degree celsius 0.19 0.20v. can't measure voltage arduino uno. , wheatstone bridge balanced properly.
i haven't added amplifier. have connected wheatstone bridge circuit directly arduino
have attached code here...
please reply me ... in need of urgently

code: [select]

int in_pin = a0;

void setup()
{
serial.begin(9600);
}
void loop(0
{

int val = analogread(in_pin);

double voltage = (5.0 / 1204.0) * val;

serial.println(voltage);
delay(500);

}

code: [select]

void loop(0
{
you haven't compiled this, have you?

code: [select]

double voltage = (5.0 / 1204.0) * val;
what "1204" refer to?

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