Patent GB-1477564-A (GB)
Title: Digital device for automatically checking carbon content  in metal with reference to temperature stops on cooling  curve
IPC: G01N33/20
Filed: 1975-09-26
Abstract: 1477564 Digital measurement of liquidus temperature INST KIBERNETIKI AKAD NAUK UKRAIN SSR 26 Sept 1975 39580/75 Heading H3H In checking the carbon content of steel by detecting the liquidus temperature stop on its cooling curve, the temperature of the steel is digitized in a reversible counter 5 incremented and decremented by pulses from a converter 4 corresponding to positive and negative temperature changes, the counter 5 being readout into a register 8 and displayed, 9, when a time interval discriminator circuit 6 has counted a predetermined number of clock pulses since the last temperature change pulse, indicating the liquidus temperature stop. If the carbon content is not linearly proportional to the liquidus temperature, a code converter 22 is included between the register 8 and display 9. In a preferred arrangement, the converter 4 is a photo-electric displacement sensor coupled to the stylus of graph plotter recording the cooling curve, Fig. 8 (not shown). Its output pulses are synchronised to fall between clock pulses by a circuit 10, details, Fig. 13 (not shown). The temperature change pulses from the converter 4 may pass through a "lost motion" counter circuit 17 for eliminating the effects of small perturbations on the cooling curve, details, Figs. 16 to 18 (not shown). The discriminator circuit 6 may include a clock pulse counter, selector switches and gates. Preferably, Fig. 11, it comprises a clockpulse counter 39 which is reset to an initial value each time it receives a pulse from the "lost motion" circuit 17 or a cycle initiating signal (24). The cooling curve includes an initial rising phase as the temperature probe warms up and the turning point at the top of this is interpreted as the liquidus temperature only if counter 39 reaches a number selected by switches 42. Otherwise, as the cooling curve falls, flip-flop 45 inhibits gate 43 and enables gate 41 so that a subsequent temperature stop is interpreted as the liquidus temperature if the counter 39 attains a number set by switches 40. If two outputs should occur from the discriminator circuit 6 (e.g. due to a supercooling turning point preceding the liquidus temperature turning point) the reading in the counter 5 at the second discriminator output is taken into the register 8 the first reading being lost. Any output from the discriminator circuit 6 is remembered by a flipflop 11 to enable a gate 14 and block 16 so that at the end of a predetermined cycle time, set by an adjustable timing counter circuit 12, details, Figs. 14 and 15 (not shown), the display 9 is energized, or if no output from discriminator circuit 6 has occurred a new cycle is initiated by circuit 15. The output of timer 12 also inhibits gate 13, blocking further clock pulses from reaching circuits 6 and 12. If an extremely long temperature stop is detected, a gate 18 is enabled to energize the display 9 without waiting for the end of the cycle timed by circuit 12. The system is automatically set to an initial state when gate 23 detects a certain value in counter 5 during the initial warm up phase. The output of code converter 22 may be used for automatic computer control of steel smelting.