Temperature characteristic determination of silicon photodiodes used in radiation pyrometry application

Optical (radiation) pyrometry-thermometry is metrology of high temperatures (over 964.78degreesC) in which both visual and near infrared spectral components dominate in radiation spectra. It is a non-contact technique of temperature measurement based on Planck's radiation law, i.e. correlation between intensity of electromagnetic radiation and temperature. Photoelectrical pyrometers with linear current characteristic in optical pyrometry are often used for reliable temperature measurements in rough industrial conductions[l]. They utilize semiconductor silicon diodes for photoelectrical detection. High linearity, sensitivity and relatively good temperature stability of these pyrometers depend on their silicon photodiode characteristics. Temperatuare variations affect temperature characteristics and dark current of diodes. This phenomena can be explained by changes in photodetector current ID which depends on temperature and wavelength[2]. Increased temperature greatly affects coefficient of output current ID variation with temperature (Klambda) for wide range of wavelengths lambda epsilon(400-1100) nm. We performed measurements on two different photodiode types: Simens BPW21 with lambda=600nm of peak sensitivity and FDO8N with lambda=900nm of peak sensitivity (producer Institut IHTM, Belgrade). These two photodiode types are commonly used for high temperature measurements in linear photoelectric optical pyrometers[3]. We propose method for characterization of Klambda and K-uk, for both types of photodiodes, and we give comparison of experimentally and theoretically obtained values for two types of wide zone optical pyrometers: lambda epsilon(400-1100) nm and lambda epsilon(700-1100) nm.