Interfacing to PT1000 w/ limited range of interest

hi all,
im not sure if right forum, seemed closest match.

i want interface arduino pt1000 rtd temperature sensor. range of interest 85c 95c corresponds 1328 ohms 1366 ohms.
i have breadboarded circuit , using 25 ohm variable resistor simulate rtd sensor.

so, reading "sensor" value, performing operation on range of values interested in , serially outputting pc. , working.....

but getting integer values, whereas want 0.1 resolution.

is possible serial output?

later interfacing lcd, maybe can on lcd?

here code....

code: [select]

/*
 rtd analog input
read value of rtd/pot, save
variable, calculate temp

circuit:
* wheatstone bridge feeds diff amp attached analog input 0


 */

int sensorvalue = 0;  // variable store value coming sensor
int tempvalue = 0; // variable store calculated temp

void setup() {
 serial.begin(9600);
}

void loop() {
 // read value sensor:
 int sensorvalue = analogread(0);
 tempvalue = ((sensorvalue-225)/54)+85;
 serial.println(tempvalue);
 delay(10);

}

any advice appreciated!

you're being bitten "integer division". in c++ 150/54 (for example) 2. not 2.777 or 2.8 2. expression ((sensorvalue-225)/54) loses lot of precision.

you can try using floats or doubles work real numbers prior converting integer:

code: [select]

tempvalue = ((sensorvalue-225.0)/54)+85;

adding real number forces real-number computation, , final result converted integer when write result tempvalue.

--
the gadget shield: accelerometer, rgb led, ir transmit/receive, light sensor, potentiometers, pushbuttons

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