Add PT1000 as temperatur sensor characteristic

[uhi22]

The charge port temperatur measurement is configurable for NTCs.
Feature request: Add the possibility to use PT1000 temperature sensors.

Discussion startet here: https://openinverter.org/forum/viewtopic.php?p=88718#p88718

Links to some data sheets of charge ports: https://openinverter.org/forum/viewtopic.php?p=88730#p88730

Next steps: Find out, whether the PT1000 is already implemented in a project where we could just copy from, e.g. Zombieverter.

[uhi22]

Result: The PT1000 code/configuration is available in https://github.com/damienmaguire/Stm32-vcu/blob/master/src/temp_meas.cpp

Next step: Find out, how to bring this into Clara software.

[uhi22]

Alternative approach (AI generated conent. Source: claude.ai)

Prompts:

1. Write a C code, which translate a resistance value (in ohm) to the temperature of a PT1000 sensor.
2. Is there a simpler approach if we need less precision? 1 Kelvin deviation is fine.

Result summary:
Linear approximation. The entire conversion function is now just one simple line:
cT = (R - R0) / (R0 × α)
Key advantages:

No math library needed (no -lm flag)
No iterations or complex calculations
Just one division operation
Very fast execution

Accuracy:

Within ±0.5°C for -50°C to +150°C range
Within ±1°C for -100°C to +200°C range
Within ±2°C for -150°C to +300°C range

Code
`// PT1000 coefficients (IEC 60751)
#define R0 1000.0 // Resistance at 0°C (ohms)
#define ALPHA 3.9083e-3 // Temperature coefficient (α)

/**

• Simple PT1000 resistance to temperature conversion
• Uses linear approximation: R(T) ≈ R0(1 + αT)
• Solving for T: T ≈ (R - R0) / (R0 * α)
• Accuracy: Within ±1°C for range -50°C to +150°C

•      Within ±3°C for range -100°C to +300°C
  

*/
double pt1000_resistance_to_temp(double resistance) {
return (resistance - R0) / (R0 * ALPHA);
}
`
Next step: Test whether this simple solution is correct

[uhi22]

Simple linear formula (thanks claude.ai) works fine in demo code:

gcc playground_PT1000_calculation.c
./a.exe

PT1000 Resistance to Temperature Converter

Resistance: 800.0 Ω → Temperature: -51.9 °C
Resistance: 1000.0 Ω → Temperature: 0.0 °C
Resistance: 1078.0 Ω → Temperature: 20.3 °C
Resistance: 1194.0 Ω → Temperature: 50.4 °C
Resistance: 1385.0 Ω → Temperature: 100.0 °C