The PT100 temperature sensor is one of the most widely used RTD (Resistance Temperature Detector) sensors in industrial and laboratory applications. Its high accuracy, stability, and reliability make it a preferred choice for precise temperature measurement across a wide range of industries.
This guide provides a detailed explanation of PT100 sensors, including their working principle, construction, characteristics, advantages, applications, and selection criteria.
What is a PT100 Temperature Sensor?
A PT100 temperature sensor is an RTD that uses a platinum element with a resistance of 100 ohms at 0°C. The "PT" stands for platinum, and "100" refers to the resistance value at 0°C. PT100 sensors are manufactured according to the IEC 60751 standard.
- Material: Platinum (Pt)
- Base Resistance: 100 ohms at 0°C
- Type: Resistance Temperature Detector (RTD)
- Standard: IEC 60751
How Does a PT100 Sensor Work?
PT100 sensors operate on the principle that the electrical resistance of platinum increases predictably with temperature. This relationship is highly linear and repeatable, making platinum ideal for temperature measurement.
Resistance-Temperature Relationship
The resistance of a PT100 sensor at temperature t (in °C) is given by:
R(t) = R₀(1 + At + Bt²)
- R(t): Resistance at temperature t
- R₀: Resistance at 0°C (100 ohms)
- A: 3.9083 × 10⁻³ °C⁻¹
- B: -5.775 × 10⁻⁷ °C⁻²
For temperatures below 0°C, a third term (C) is added for greater accuracy.
Measurement Process
- A small, constant current is passed through the platinum element.
- The voltage drop across the element is measured.
- Resistance is calculated using Ohm's Law (R = V/I).
- The resistance value is converted to temperature using calibration curves.
PT100 Sensor Construction
PT100 sensors are constructed to ensure accuracy, stability, and durability in various environments.
- Platinum Element: Pure platinum wire or thin film
- Support Structure: Ceramic or glass substrate
- Protective Sheath: Stainless steel or other materials
- Lead Wires: Copper or platinum extension wires
- Insulation: High-temperature insulation materials
Key Characteristics of PT100 Sensors
- High Accuracy: ±0.1°C to ±1°C depending on class
- Excellent Stability: Minimal drift over time
- Linearity: Highly linear response
- Wide Temperature Range: -200°C to +850°C
- Interchangeability: Standardized resistance-temperature relationship
- Long Service Life: 10+ years in most applications
- Chemical Resistance: Platinum is chemically stable
Advantages of PT100 Temperature Sensors
- High Accuracy and Stability: Suitable for critical applications
- Repeatability: Consistent measurements over time
- Wide Operating Range: Suitable for extreme temperatures
- Industry Standard: Widely accepted and supported
- Multiple Configurations: 2-wire, 3-wire, and 4-wire options
- Robust Construction: Durable in harsh environments
Applications of PT100 Sensors
- Industrial Process Control: Manufacturing, chemical, and power plants
- Laboratory Equipment: Calibration and scientific research
- HVAC Systems: Building automation and climate control
- Food Processing: Cooking, pasteurization, and storage monitoring
- Pharmaceutical Manufacturing: Sterilization and drying processes
- Automotive: Engine and climate control systems
- Medical Devices: Patient monitoring and diagnostic equipment
PT100 Specifications and Standards
| Parameter | Value | Description |
|---|---|---|
| Base Resistance (R₀) | 100 Ω | Resistance at 0°C |
| Temperature Coefficient | 0.385 Ω/°C | Average TCR from 0°C to 100°C |
| Class A Accuracy | ±0.15°C | At 0°C |
| Class B Accuracy | ±0.3°C | At 0°C |
| Temperature Range | -200°C to +850°C | Standard range |
| Response Time | 1-10 seconds | Depends on construction |
PT100 Selection Criteria
- Temperature Range: Ensure the sensor covers your full temperature range
- Accuracy Requirements: Match accuracy to process needs
- Wiring Configuration: 2-wire, 3-wire, or 4-wire
- Environmental Conditions: Chemical, mechanical, and electrical factors
- Installation Requirements: Mounting style, cable length, and accessibility
- Cost: Balance performance with budget
Frequently Asked Questions
What is a PT100 temperature sensor?
A PT100 temperature sensor is a type of RTD (Resistance Temperature Detector) that uses a platinum element with 100 ohms resistance at 0°C. It measures temperature by detecting changes in electrical resistance as temperature varies, providing high accuracy and stability.
How does a PT100 sensor work?
PT100 sensors work on the principle that platinum's electrical resistance increases predictably with temperature. A small current is passed through the platinum element, and the resulting voltage drop is measured. The resistance is calculated and converted to temperature using standardized calibration curves.
What are the main applications of PT100 sensors?
PT100 sensors are used in industrial process control, laboratory equipment, HVAC systems, food processing, power generation, pharmaceutical manufacturing, and any application requiring accurate and stable temperature measurement.
What is the accuracy of PT100 sensors?
PT100 accuracy ranges from ±0.1°C to ±1°C depending on the class (A, B, C, D) and wiring configuration. Class A offers ±0.15°C, Class B ±0.3°C, and 4-wire configurations can achieve ±0.1°C or better.
What is the temperature range of PT100 sensors?
PT100 sensors typically operate from -200°C to +850°C, with the most common industrial range being -50°C to +400°C.
How do I choose the right PT100 sensor?
Consider temperature range, required accuracy, environmental conditions, wiring configuration (2-wire, 3-wire, or 4-wire), installation requirements, and cost. Match the sensor's specifications to your application's needs.
Conclusion
PT100 temperature sensors are the gold standard for accurate, stable, and reliable temperature measurement in industrial, laboratory, and commercial applications. Their standardized design, predictable performance, and proven track record make them the preferred choice for critical temperature measurement needs.
By understanding the working principle, construction, characteristics, and selection criteria of PT100 sensors, you can make informed decisions and ensure optimal performance in your temperature measurement systems.