The PyroUSB Series infrared sensors are designed to measure surface temperatures without contact, offering a versatile solution for various industrial and scientific applications. These sensors provide a linear 2-wire 4 to 20 mA output, ensuring compatibility with a wide range of indicators, controllers, recorders, or data loggers without requiring special interfacing or signal conditioning. This simplifies integration into existing systems and streamlines data acquisition.
A key feature of the PyroUSB Series is the availability of different models tailored to specific measurement needs. General-purpose PUA8 (8-14 µm) models are suitable for measuring temperatures from -40°C to 1000°C. They are particularly effective for high-emissivity materials such as paper, thick plastics, food products, pharmaceuticals, rubber, asphalt, and painted surfaces. For applications involving low-emissivity materials like many reflective metals, or for measuring through glass viewports, the short-wavelength PUA2 (2.2 µm) models are available, offering temperature ranges from 45°C to 2000°C. These models provide more accurate readings in such challenging environments. Additionally, Glass PUA5 (5 µm) models are specifically filtered at a wavelength where glass is least reflective, making them ideal for glass surface temperature measurement with a range from 200°C to 1650°C. This selection of models ensures that users can choose the most appropriate sensor for their specific material and temperature requirements.
The installation process for PyroUSB sensors involves several stages: preparation, mechanical installation, and electrical installation. Proper preparation is crucial, ensuring the sensor is positioned to focus solely on the target. The measured spot size must be smaller than the target to ensure accurate readings. Reflective surfaces from lamps, heaters, or sunlight can interfere with measurements, so the sensor should be installed in a location that minimizes such reflections, with shields potentially being helpful. The sensor is designed to operate in ambient temperatures from 0°C to 70°C, but for temperatures above 70°C, an air/water-cooled housing is required. Avoiding thermal shock and allowing 20 minutes for the unit to adjust to large ambient temperature changes are also important for optimal performance. Atmospheric quality can also impact accuracy; smoke, fumes, or dust can contaminate the lens, necessitating the use of an air purge collar to keep the lens clean in such environments. To minimize electromagnetic interference, the sensor should be mounted away from motors, generators, and similar equipment.
Mechanically, all sensors come with a 1m cable and a mounting nut, allowing for installation on custom brackets or using fixed and adjustable mounting bracket accessories. For high ambient temperatures, an optional air/water cooled housing can be used. This housing is equipped with two 1/8″ BSP fittings, and water temperature should ideally be between 10°C and 27°C for efficient cooling. Chilled water below 10°C is not recommended, and an air purge collar should be used with the water-cooled housing to prevent condensation. The water flow rate should be adjusted to keep the sensor body between 0°C and 70°C. The air purge collar itself is designed to keep dust, fumes, moisture, and other contaminants away from the lens, requiring an air flow of 5 to 15 litres/min, with clean or 'instrument' air recommended.
Electrically, the sensor offers flexible connection options. It can operate with either the 4-20 mA cable connected, the USB cable connected, or both. For the 4-20 mA output, the sensor connects to a controller/indicator with a 24 V DC power supply in the loop, with a maximum loop impedance of 900 ohms. It's crucial to ground the sensor at only one point, either the cable shield or the sensor housing. When using the USB output, no external power supply is required, as the sensor is powered via the USB cable. However, it is critical to use only the supplied USB cable, as using any other type may damage the sensor and invalidate the warranty. The software must be installed before connecting the sensor to a PC.
Configuration of the sensor is done via CalexConfig software, with settings protected by a default password. Users can switch between Celsius and Fahrenheit temperature units. Output processing allows setting the 4-20 mA output scale, ensuring the temperature range on the measurement instrument matches the sensor's output scale. An averaging period can be set to prevent the sensor from following rapid temperature changes. Peak/valley hold processing is useful when temperature readings are interrupted by gaps between moving objects or obstructions. Emissivity settings can be adjusted based on the target material, and window transmissivity can be set if the sensor is aimed through an IR-transmissive window. Reflected energy compensation can be enabled to account for errors from hotter or colder surrounding objects, with the reflected temperature also being configurable.
Maintenance of the PyroUSB sensor is straightforward. The lens should be kept clean at all times, as foreign matter can affect measurement accuracy. Loose particles can be blown off with an air 'puffer' if an air purge accessory is not in use. If the sensor is exposed to significant changes in ambient temperature, allowing 20 minutes for stabilization before taking measurements is recommended. It's important not to operate the sensor near large electromagnetic fields and to connect wires only to the appropriate terminals. Opening the sensor housing will damage the sensor and invalidate the warranty. Calex provides customer service for application assistance, calibration, repair, and troubleshooting, with a two-year guarantee against defects in material and workmanship.
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