Thermocouples

A comprehensive, high-accuracy thermocouple calculation library for Python with clean object-oriented architecture and professional API design that hides implementation details.

Features

• 🎯 Temperature to Voltage Conversion: Convert temperature (°C) to thermoelectric voltage (V)
• 🌡️ Voltage to Temperature Conversion: Convert voltage (V) to temperature (°C)
• 📊 Seebeck Coefficient Calculation: Get the Seebeck coefficient (µV/K) at any temperature
• 📈 Temperature Derivative of Seebeck: Calculate dSeebeck/dT (nV/K²) for advanced analysis
• ❄️ Cold Junction Compensation: Built-in volt_to_temp_with_cjc() method for reference junction temperature compensation
• 🔬 Individual Thermocouple Leg Calculations:
  • Voltage calculations for positive and negative legs separately
  • Seebeck coefficient calculations for positive and negative legs separately
• 🎯 High Accuracy: Based on NIST Monograph 175 polynomial coefficients
• ✅ All Standard Types: Supports B, E, J, K, N, R, S, and T type thermocouples
• 🐍 Pure Python: No external dependencies required
• 🏗️ Modern OOP Architecture: Clean, maintainable object-oriented design
• 🧪 Well Tested: Comprehensive test suite ensuring accuracy
• 📚 Type Safe: Full type hints for better IDE support

What's New in Version 2.1

🧹 Professional API Cleanup:

• Clean Interface: All internal implementation details hidden with underscore prefixes
• IDE-Friendly: Only user-relevant methods visible in autocomplete
• Simplified Functions: Shortened method names (temp_to_volt vs temperature_to_voltage)
• Pure OOP Design: Complete removal of legacy function-based API
• Professional Standards: Following Python best practices for library design

Supported Thermocouple Types

Type	Temperature Range	Materials	Application
B	0°C to 1820°C	Pt-30%Rh / Pt-6%Rh	Ultra-high temperature
E	-270°C to 1000°C	Ni-Cr / Cu-Ni	Highest sensitivity
K	-270°C to 1372°C	Ni-Cr / Ni-Al	Most popular, general purpose
N	-270°C to 1300°C	Ni-Cr-Si / Ni-Si	Improved K-type
R	-50°C to 1768°C	Pt-13%Rh / Pt	High temperature, precious metal
S	-50°C to 1768°C	Pt-10%Rh / Pt	High temperature, precious metal
T	-270°C to 400°C	Cu / Cu-Ni	Cryogenic applications

Quick Start

Installation

pip install thermocouples

Basic Usage (New OOP API - Recommended)

import thermocouples as tc

# Create thermocouple instance
tc_k = tc.get_thermocouple("K")

# Temperature to voltage conversion
voltage = tc_k.temp_to_volt(100.0)  # 4.096 mV at 100°C
print(f"K-type at 100°C: {voltage:.3f} mV")

# Voltage to temperature conversion  
temperature = tc_k.volt_to_temp(0.004096)  # Back to ~100°C
print(f"K-type at 4.096 mV: {temperature:.1f}°C")

# Seebeck coefficient calculation
seebeck = tc_k.temp_to_seebeck(100.0)  # µV/K
print(f"Seebeck coefficient at 100°C: {seebeck:.1f} µV/K")

Advanced Usage

import thermocouples as tc

# Get a thermocouple instance
tc_k = tc.get_thermocouple("K")

# High-precision calculations
voltage = tc_k.temp_to_volt(200.5)
seebeck = tc_k.temp_to_seebeck(200.5)  # Seebeck coefficient
dsdt = tc_k.temp_to_dsdt(200.5)        # Temperature derivative

# Cold junction compensation
hot_junction_temp = 500.0  # °C
cold_junction_temp = 25.0   # °C (room temperature)

# Method 1: Built-in Cold Junction Compensation (Recommended)
measured_voltage = 0.019665  # V (voltage measured by your instrument)
actual_temp = tc_k.volt_to_temp_with_cjc(measured_voltage, cold_junction_temp)
print(f"Actual temperature: {actual_temp:.1f}°C")

# Method 2: Manual calculation (for understanding)
voltage_hot = tc_k.temp_to_volt(hot_junction_temp)
voltage_cold = tc_k.temp_to_volt(cold_junction_temp)
expected_measurement = voltage_hot - voltage_cold
print(f"Expected measured voltage: {expected_measurement:.6f} V")

# Verify with built-in CJC function
calculated_temp = tc_k.volt_to_temp_with_cjc(expected_measurement, cold_junction_temp)
print(f"Calculated temperature: {calculated_temp:.1f}°C")

# Individual thermocouple leg analysis
tc_e = tc.get_thermocouple("E")

# Positive leg (Ni-Cr) calculations
pos_voltage = tc_e.temp_to_volt_pos_leg(300.0)
pos_seebeck = tc_e.temp_to_seebeck_pos_leg(300.0)

# Negative leg (Cu-Ni) calculations  
neg_voltage = tc_e.temp_to_volt_neg_leg(300.0)
neg_seebeck = tc_e.temp_to_seebeck_neg_leg(300.0)

print(f"E-type at 300°C:")
print(f"  Positive leg: {pos_voltage:.6f} V, {pos_seebeck:.3f} µV/K")
print(f"  Negative leg: {neg_voltage:.6f} V, {neg_seebeck:.3f} µV/K")
print(f"  Difference:   {pos_voltage - neg_voltage:.6f} V")

Working with Multiple Types

import thermocouples as tc

# Compare different thermocouple types at the same temperature
temperature = 400.0  # °C
types = ["B", "E", "J", "K", "N", "R", "S", "T"]

print(f"Voltages at {temperature}°C:")
for tc_type in types:
    if tc_type == "B" and temperature < 250:
        continue  # B-type has limited range at low temperatures
    
    thermocouple = tc.get_thermocouple(tc_type)
    voltage = thermocouple.temp_to_volt(temperature)
    seebeck = thermocouple.temp_to_seebeck(temperature)
    print(f"  Type {tc_type}: {voltage:.6f} V (Seebeck: {seebeck:.1f} µV/K)")

Architecture Overview

Version 2.0 features a clean object-oriented architecture:

thermocouples/
├── base.py              # Abstract base class with common calculation logic
├── registry.py          # Factory functions for creating thermocouple instances  
├── types/
│   ├── type_b_class.py  # B-type thermocouple implementation
│   ├── type_e_class.py  # E-type thermocouple implementation
│   ├── type_j_class.py  # J-type thermocouple implementation
│   ├── type_k_class.py  # K-type thermocouple implementation
│   ├── type_n_class.py  # N-type thermocouple implementation
│   ├── type_r_class.py  # R-type thermocouple implementation
│   ├── type_s_class.py  # S-type thermocouple implementation
│   └── type_t_class.py  # T-type thermocouple implementation
└── __init__.py          # Public API with backward compatibility

Each thermocouple type inherits from the abstract Thermocouple base class, ensuring:

• Consistent Interface: All types support the same methods
• Code Reuse: Common calculation logic is shared
• Type Safety: Full Python type hints throughout
• Extensibility: Adding new types is straightforward

API Reference

Factory Functions

• get_thermocouple(tc_type: str) -> Thermocouple: Get a thermocouple instance

Thermocouple Class Methods

Each thermocouple instance provides:

Core Conversion Methods

• temp_to_volt(temperature: float) -> float
• volt_to_temp(voltage: float) -> float
• volt_to_temp_with_cjc(voltage: float, ref_temp: float) -> float
• temp_to_seebeck(temperature: float) -> float
• temp_to_dsdt(temperature: float) -> float

Individual Leg Methods

• temp_to_volt_pos_leg(temperature: float) -> float
• temp_to_volt_neg_leg(temperature: float) -> float
• temp_to_seebeck_pos_leg(temperature: float) -> float
• temp_to_seebeck_neg_leg(temperature: float) -> float

Properties

• name: str - Thermocouple type identifier (e.g., "Type K")

Requirements

• Python: 3.9+
• Dependencies: None (pure Python implementation)

Accuracy and Validation

This library implements the official NIST ITS-90 thermocouple equations from NIST Monograph 175 with rigorous precision:

• Temperature-to-Voltage: Polynomial evaluation using NIST coefficients
• Voltage-to-Temperature: Iterative solution with Newton-Raphson method
• Individual Leg Calculations: Separate positive and negative leg polynomials
• Exponential Corrections: Applied for specific types (K, N) where required
• High Precision: Maintains accuracy within NIST tolerance specifications

Temperature Ranges by Type

Type	Lower Limit	Upper Limit	Note
B	0°C	1820°C	Limited accuracy below 250°C
E	-270°C	1000°C	Highest sensitivity of all types
J	-210°C	1200°C	Iron oxidizes above 750°C in air
K	-270°C	1372°C	Most common general-purpose type
N	-270°C	1300°C	Improved drift characteristics vs. K
R	-50°C	1768°C	Precious metal, high temperature
S	-50°C	1768°C	Precious metal, similar to R
T	-270°C	400°C	Excellent for cryogenic applications

Installation & Testing

Install from PyPI

pip install thermocouples

Run Built-in Tests

# Quick validation test
python -c "import thermocouples as tc; print('✓ Library loaded successfully')"

# Compare multiple types
python -c "
import thermocouples as tc
for t in ['K', 'J', 'T']:
    tc_obj = tc.get_thermocouple(t)
    v = tc_obj.temp_to_volt(100.0)
    print(f'Type {t}: {v:.6f} V at 100°C')
"

Migration Guide

Version 2.1 uses a clean OOP-only API. Here's how to use the new simplified interface:

# Modern API (clean, professional)
import thermocouples as tc
tc_k = tc.get_thermocouple("K")
voltage = tc_k.temp_to_volt(100.0)
temperature = tc_k.volt_to_temp(0.004096)

The clean OOP approach offers:

• Better Performance: Instantiate once, use many times
• Type Safety: Full Python type hints
• IDE Support: Only relevant methods visible in autocomplete
• Code Clarity: Professional object-oriented interface
• Clean Design: Implementation details hidden from user view

Contributors

• Version 2.1 Architecture - Clean API with hidden implementation details

License

MIT License - see LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. Areas for contribution:

• Additional thermocouple types (C, G, M, etc.)
• Performance optimizations
• Enhanced documentation
• Test coverage improvements

Disclaimer

⚠️ Important: While this library implements NIST-standard calculations with high precision, users are responsible for validating results for their specific applications. For critical measurements or safety-related applications, please refer directly to NIST Monograph 175 or conduct independent verification.

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