Metal processing is one of the most demanding industrial applications for temperature sensors, with high temperatures, harsh environments, and strict accuracy requirements. PT100 3-wire sensors are widely used in metal processing because of their ability to withstand high temperatures (up to 850°C), high accuracy, and stability. However, metal processing environments present unique challenges-including extreme heat, corrosive gases, and vibration-that can affect sensor performance. According to experience, PT100 3-wire connections are the best choice for metal processing, but they must be selected and installed correctly to withstand these harsh conditions.
Metal processing applications-including forging, casting, rolling, and heat treatment-require precise temperature control to ensure the metal's properties (strength, hardness, ductility) are consistent. For example, heat treatment involves heating metal to a specific temperature (often 500-800°C) and cooling it at a controlled rate to achieve the desired properties. A 1°C error in temperature can affect the metal's hardness, leading to product defects. PT100 3-wire sensors provide accuracy within ±0.1°C (for A级 sensors), which is essential for meeting these strict requirements.
The 3-wire connection is particularly important in metal processing because the sensor wires are often long (20-50 meters) due to the size of the processing equipment. Wire resistance errors would otherwise cause significant inaccuracies-for example, a 0.5-ohm wire resistance can lead to a 1.3°C error, which is enough to affect the metal's properties. The 3-wire method eliminates these errors by using three identical wires, ensuring the instrument only measures the sensor's resistance, not the wire resistance.
Sensor selection is critical in metal processing. The sensor's sheath material must be able to withstand high temperatures and corrosive gases. 316 stainless steel is suitable for temperatures up to 600°C, but for higher temperatures (600-850°C), Hastelloy or Inconel sheaths are recommended. These materials are resistant to high temperatures, corrosion, and oxidation, ensuring the sensor remains durable in harsh metal processing environments. Additionally, the sensor should have a high-temperature insulation (like magnesium oxide) to prevent short circuits at high temperatures.
Wire selection is another important consideration. The wires must be able to withstand high temperatures (up to 200°C or higher) and resist corrosion. Teflon-coated copper or stainless steel wires are ideal, as they are heat-resistant and corrosion-resistant. All three wires must be identical in material, gauge, and length to ensure the 3-wire method works properly. For longer wire runs (over 20 meters), 1.0mm² or 1.5mm² wires are recommended to keep resistance low.
Sensor placement is crucial in metal processing to ensure accurate temperature measurement. In heat treatment furnaces, the sensor's probe must be inserted into the furnace chamber, away from direct heat sources (like heating elements) and cold spots. The probe should be inserted to a minimum depth of 200mm to ensure it measures the temperature of the furnace atmosphere, not the probe itself. In rolling or forging applications, the sensor should be placed near the metal surface to measure the metal's temperature during processing.
Vibration is a common issue in metal processing, as equipment like rolling mills and forging presses generate significant vibration. Vibration can loosen connections, damage the sensor's probe, or break the wires. To mitigate vibration, use vibration-resistant sensors with sturdy mounting brackets. Secure the wires with cable ties to prevent them from moving or rubbing against equipment. Additionally, use stranded wires instead of solid wires, as they are more flexible and resistant to vibration damage.
Calibration is essential in metal processing to ensure the sensor's accuracy. High temperatures and harsh conditions can cause sensor drift over time, leading to inaccurate readings. PT100 3-wire sensors should be calibrated every 6 months, or more frequently if the processing is critical. Calibration involves comparing the sensor's readings to a calibrated reference thermometer (capable of withstanding high temperatures) and adjusting the instrument accordingly. This ensures the sensor provides accurate readings throughout the metal processing process.
Many metal processing facilities make the mistake of using thermocouples instead of PT100 3-wire sensors, thinking they are more suitable for high temperatures. While thermocouples can withstand higher temperatures (up to 1700°C), they have lower accuracy (±1-2°C), which is not sufficient for precision metal processing. PT100 3-wire sensors provide higher accuracy and are suitable for temperatures up to 850°C, which covers most metal processing applications.
Maintenance is also important in metal processing. The sensor's probe can become coated with metal oxide or scale, which blocks heat transfer and leads to inaccurate readings. Regular cleaning with a wire brush or abrasive pad removes this buildup and ensures accurate readings. The wires and connections should also be inspected regularly for signs of damage or corrosion-if corrosion is found, the wires should be replaced immediately to avoid errors.
In summary, PT100 3-wire connections are the ideal choice for metal processing, providing accurate temperature measurement and withstanding high temperatures and harsh conditions. By choosing the right sensor (with high-temperature sheath material), proper wire selection, correct sensor placement, and regular calibration and maintenance, metal processing facilities can ensure consistent product quality and reduce defects. For complex metal processing applications, professional heating solution providers can offer customized sensor solutions to meet specific temperature control requirements.
