Infrared Temperature Sensors

Infrared temperature sensors from the Calex PyroCouple Series are being used by a major tyre manufacturer to detect the presence of hot rubber tire material as it passes a point on a conveyor. The tyre material is transported in two thin bands on a cooled aluminum conveyor. A PyroCouple model PC301MT-0 infrared temperature sensor is positioned above the conveyor, and is aimed so that both bands are contained in its field of view. The temperature of the tire material is normally 75°C and the cooled conveyor surface temperature is typically 20°C. The sensor is connected to a DIN rail-mounted controller with a relay output that will switch at a chosen measured temperature (e.g. about 45°C). The relay set point temperature is low enough that the relay will be triggered reliably despite the tire material not completely filling the sensor's field of view. The system can therefore detect the presence of the tire material, and the time that the material starts and stops being present can be logged. Speed data from the conveyor drive system is combined with the timings from the sensor and the total length of tire material passing the sensor can be calculated over each manufacturing period. This system can also be used to detect the presence of a single band of product. If the sensor's field of view is completely filled by the tire material, then the temperature reading will also be accurate. Tire rubber has a high emissivity, so the low-cost, fixed-emissivity PyroCouple Series of infrared temperature sensors is perfectly suitable. The sensor measures an average temperature across its field of view. Because the sensor can also "see" the cool conveyor as well as the hot tire material, the measured temperature will be lower than the true temperature of the tire material, however the reading is sufficiently accurate that the sensor may be used to detect whether or not it is present. The PPT245 DIN rail-mounted controller will indicate the measured temperature and the set point temperature, and can also be configured to retransmit the measured temperature as a linear 0-10 V DC or 4-20 mA signal for connection to a data logger or instrumentation. It has another relay output that can be configured for control or alarm.