The PRO 40 Single-Wavelength Sensors with Visual Alignment are used to measure most common materials in general purpose applications. The PRO 42 models feature a unique auto null design that enables more accurate measurements on applications such as cold rolled steal and low temperature induction heating processes where the temperatures can go as low as 100°F (40°C) and the surface has a low or varying emissivity. For most applications, the selection of the sensor is based on the temperature range and the optics that meet the requirements of the application. However, some applications require careful selection of the sensor's operating wavelength in order to obtain accurate measurements. Frequently, the selection of a specific narrow band filter will result in a narrower temperature range for the sensor, but the benefit can be dramatic improvements in the accuracy and repeatability of temperature measurements.