Total radiation pyrometer

Total Radiation Pyrometers In total radiation pyrometers, the thermal radiation is detec ted over a large range of wavelengths from the objec t at high temperature. The detector is normally a thermopile, which is built by connec ting several thermocouples in series to increase the temperature measurement range. The pyrometer is calibrated for black bodies, so the indicated temperature Tp should be converted for non-black body temperature. 

The Broadband Radiation Thermometer (Total Radiation Pyrometer)... 

While disappearing filament pyrometers are convenient and accurate, they require human interaction and hence are not well suited for use in feedback control systems. In a total radiation pyrometer, a lens system focuses incoming radiation onto... 

Later developments in temperature measurement employed knowledge about the relationship between temperature and radiation emission, measurable on a spectrometer. Probably first used by H. Le Chatelier in 1892, such a device was termed an optical pyrometer. Another temperature-measuring instrument based on radiation from a hot surface was the total radiation pyrometer. This device was proposed by C. Fery in 1902 and modified by others (Fery, 1902). 

Radiation thermometers were developed for measuring temperatures higher than 1064°C they have the advantage that they are noncontact thermometers. Optical pyrometers measure apparent temperatures of objects by comparing the radiation from the objects over a narrow wavelength band with that of a standard, preferably using a photoelectric detector for the comparison. Corrections for the emissivity of the source must be made to determine the temperature the preceived temperature may be, and usually is, lower because all of the heat is not radiated. Total-radiation pyrometers measure the whole spectrum of energy radiated by the source. They are less accurate than optical pyrometers but can measure much lower temperatures (of the order of 100°C). This type of pyrometer also requires emissivity corrections. 

Another instrument is based on focusing the total radiation emitted by the measured body on a blackened thermopile by means of a quartz lens. The e.m.f. of the thermopile then gives the temperature. Both the optical and the total radiation pyrometers are commercially available and are very convenient and easy to use. 

Optical pyrometers can be used for temperature ranges of 760-3500°C [4]. In special cases (narrow-band and total radiation pyrometers) they can be used for much lower temperatures (between —40 and 4-4000° C) if a non-contact measurement is desired [4]. 

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