GB676864A - Improvements in or relating to temperature indicating apparatus - Google Patents

Abstract

676,864. Photo-electric temperature indicating systems. GALL, D. C., and KITSON, W. June 1, 1949 [May 5, 1948], No. 12398/48. Addition to 624,641. Class 40 (iii). In a temperature measuring system of the type described in the parent Specification an instrument which indicates the response of a radiant heat sensitive element modifies the response of the element to the radiant energy so as to produce a desired relationship between source temperature and meter indication. In the Figure, the output of a barrier layer type cell 1 is amplified at 5a and feeds series-connected coils 7, 13 of a pair of moving coil instruments. Coil 7 moves a coloured indicator 8 of the type described in the parent Specification to give a visual indication of the furnace colour. Coil 13 interposes an optical wedge 12 into the beam of radiant energy to reduce the photo-cell response, the construction of the wedge determining the law relating furnace temperature to indicator position. To make the indicator more quick acting, and to prevent overswing, wipers tap voltages from potentiometers 15, 16 which oppose the photocell output and are fed through further coils 7a, 13a operating under the same conditions as coils 7, 13. These coils 7a, 13a may, if desired, be used without the potentiometers. It is stated that the optical wedge 12 may be omitted and the potentiometers relied on to produce the necessary feed-back. In the embodiment of Fig. 1 (not shown), in which only the optical feed-back system is used a variable resistance type photo-cell feeds an amplifier which comprises an A.C. fed thyratron. Alternatively the amplifier circuit of Specification 585,419 or a magnetic amplifier may be used. In the embodiment of Fig. 3 (not shown) a single movement fulfils the dual function of temperature indicator and feed-back means, this movement carrying both a graduated screen to reduce the radiant energy reaching a bolometer and a pointer.