GB744914A - Improvements in or relating to radiation pyrometers - Google Patents

Abstract

744,914. Radiation pyrometers. LAND PYROMETERS, Ltd. March 15, 1954 [March 21, 1953], No. 7843/53. Class 40 (3). In a radiation pyrometer suitable for measuring the temperature of molten glass use is made of infra-red radiation to which the glass is opaque. A pair of detectors connected in opposition being so disposed that both receive radiation from the hot source but one of the receivers having in its path a screen opaque to radiation in the long wavelength part of the infra-red spectrum. Thus the difference in output of the two cells indicates the red intensity of the lower wavelengths only. As shown, radiation from the hot body 5 passes through a fluorite window 6 transmitting as shown in the dotted curve (Fig. 1) to a thermopile 9 with strips sufficiently widely spaced to allow radiation to pass between them to a second thermopile 11. Between the two thermopiles is situated a silica window 10 having a transmissivity as shown in curve 1 of Fig. 1. This 'thermocouple is shunted by a resistor 12 which enables the relative sensitivities of the thermocouples to be adjusted. A thermistor 15 in series with the thermocouples and mounted on plate 14 corrects for ambient temperature while a further thermocouple comprising copper leads 17 and a suitable wire 17A joined at an insulating screw 17B attached to plate 7 corrects for heating of the plate. The assembly on which the thermocouples are mounted is adjustable over studs 20 against the action of springs 22 by nuts 21. In a modification (Fig. 5, not shown) an arrangement described in Specification 681,835 is used in which the end of the instrument near the hot body is provided by a polished concavity in which is a central fluorite window. This cavity when placed near the heated body produces black body conditions. In Fig. 6 (not shown) the housing is spaced from the hot body a fluorite lens being provided to direct the heat on to the thermopile. In Fig. 7 (not shown) the two thermocouples are situated side by side with a single fluorite window directing radiation on to both while in Fig. 8 (not shown) the thermocouples are each situated in a separate housing provided with a fluorite focusing lens. Photocells or polometers may be used instead of thermocouples.