Hello,

Linearisation is likely done in the transmitter.
There are two calibration scews (potentiometers) on the transmitter.
The following picture shows wich screw has the function of offset (o) and gain:

View attachment 120912

You will need two known temperatures to calibrate.
Usualy melting ice (0 °C) and boiling water (100 °C) are used.

Bertus

so how the equation will look like to find the temperature if i am using 100ohm

 

Hello,

What is the input range of the used ADC?
The formula depends on which ADC values you will see at 0.4 Volts and 2 Volts.

Bertus

 

Hello,

What is the input range of the used ADC?
The formula depends on which ADC values you will see at 0.4 Volts and 2 Volts.

Bertus

void setup() {
// put your setup code here, to run once:
pinMode(A0,INPUT);
Serial.begin(9600);
}
float prev = 17;
void loop() {
// put your main code here, to run repeatedly:
float v=analogRead(A0);

float V=v/1024.5*5.0;

float T=-50+(V-0.4)*(150+50)/(2-0.4);

float T_new = 0.75*prev + 0.25*T;
prev = T_new;
Serial.println(T_new);
delay(100);
}

 

it worked now

 

Hello,

As I asked, what is the range of the used ADC?
If you only use 2 volts range on a 5 Volts ADC, you will loose resolution.
When you use a 250 Ohms resistor, the transmitter will put out between 1 and 5 Volts.
The 250 Ohms can easily be made with 4 1K resistors in parallel.

Bertus

 

The 250 Ohms can easily be made with 4 1K resistors in parallel.

Or a 270Ω in parallel with 3.3kΩ

 

Hello,

As I asked, what is the range of the used ADC?
If you only use 2 volts range on a 5 Volts ADC, you will loose resolution.
When you use a 250 Ohms resistor, the transmitter will put out between 1 and 5 Volts.
The 250 Ohms can easily be made with 4 1K resistors in parallel.

Bertus

i supply the transmitter with 24v

 

Hello,

But the transmitter puts out current from 4 to 20 mA.
When you use a resistor of 100 Ohms that will give you a voltage range of 0.4 to 2 Volts.
With a 250 Ohms resitor the voltage raneg will be from 1 to 5 Volts.

Bertus