PT1000 temperature sensor chart & calculations (C codes)

 

What is PT1000 type sensor?

PT1000 is a platinum resistance thermometer (PRTs). It offers to sense -200 to +850 degree centigrade with high accuracy. Various manufacturer offer to different types minimum to maximum working conditions, different error percentages.

The working procedure of pt1000 sensor is vary platinum aliment's resistance according to temperature. We can measure temperature to find the aliment resistance. Basically sensor has 1000Ω resistance at the 0°C. So we say it PT1000, other sensors like PT100 has 100Ω at 0°C. 

PT1000 temperature vs resistance chart :- https://drive.google.com/file/d/0B886Kbl42IVuMmhXTTluV1NTTjg/view?usp=sharing

Temperature Calculation

Temperature is proportional to sensor resistance value with a little error percentage. We can get accurate temperature with given below linearization equation.

As PRT’s are not completely linear polynomial approximation is required. In the range -200°C ≤ ϑ < 0°C electrical resistance at temperature t is calculated according to the polynomial:

In the range of 0°C ≤ ϑ ≤ 850°C coefficient c is set to zero and the polynomial becomes:

For conversion of electrical resistance to temperature the above equations can be used after solving for t:

Polynomial coefficients for conversion of resistance to temperature, or vice versa, from platinum resistance thermometers according to IPTS-68 and ITS-90 scale.

Coefficient        IPTS-68                      ITS-90
     a               +3.90802E-03            +3.9083E-03
     b               -5.80195E-07             -5.7750E-07
     c                -4.27350E-12             -4.1830E-12

Where constants A, B, and C are derived from experimentally determined parameters α, β, and δ

using resistance measurements made at 0 °C, 100 °C and 260 °C.

The self-heating of an RTD sensor is most often expressed in mW/°C, which refers to the power required to raise the internal element temperature 1°C. Thus, the higher this figure, the lower the self-heating will be. For example, assume that 2mA of excitation current is used to drive a 100Ω platinum RTD at 100°C. This produces a sensor resistance of 138.5 Ω. Its self-heating specification is 50mW/°C in water moving at 1m/second.
It is important to note that the effective self-heating of an element depends strongly on the medium in which it is immersed. For example, an RTD can self heat 100x higher in still air than in the moving water to which this specification applied.

C codes :-

#include <math.h>

float ADC()

{

                float Resistance, Add_To;

                ADCON0=0x01;       // Use AN0 (10 bit ADC) for sensor input

                ADCON0bits.GO = TRUE;

                while( ADCON0bits.GO == TRUE );

                Add_To = 1024 - (ADRESL + (ADRESH * 256 ));

                Add_To = 1024 / Add_To;

                Resistance = 1000.0 * (Add_To - 1);

                return Resistance;          

}

void Calculate_Temp(float R)

{

                float A = 3.9083E-3;

                float B = -5.775E-7;

                float T;

                R = R / 1000;       // We multiplied resistance with 1000 in 

                                              ADC() function. So need to divide with 1000.

                // T = (0.0-A + sqrt((A*A)-4.0*B*(1.0-R)))/2.0*B;

                // Break equation in small pieces

                T = 0.0 - A;

                T += sqrt((A * A)-4.0 * B * (1.0 - R));

                T /= 2.0 * B;

                temp = T;             // Actual temperature value                                      

}

If you have any question, ask feel free. I will totally devoted for your help.