GB1221419A - Temperature control apparatus - Google Patents

Abstract

1,221,419. Automatic temperature control systems. PERKIN-ELMER Ltd. March 28, 1968 [March 2, 1967], No. 9859/67. Heading G3R. An apparatus for the temperature control of an inner zone of a substantial thermal mass e.g. the working gap zone of a barrel shaped permanent magnet comprises a thermally insulating outer enclosure housing a thermally insulating partition means forming the boundary of a utilization space, the partition means being spaced from the enclosure so as to define an intermediate buffer zone, and the partition means having inflow and outflow openings, heating means cooperating with an impeller adjacent to the inflow opening for circulating a temperature regulating fluid through the utilization space and back through the buffer space, and multiple temperature sensing means providing additive electrical outputs representing the temperatures in the utilization space i.e. the inflow opening and the outflow opening, also in the buffer space intermediate between the two openings, controlling the heating means. The outer enclosure and partition means are represented by boxes 1, 2 having an inflow opening 5 and outflow opening 6. An impeller 7 is driven by synchronous motor 10 and is surrounded by a heating coil 11. Inflow temperature sensors 12A, 12B are mounted in one arm of a bridge circuit fed with alternating current, and outflow temperature sensors 13A, 13B and buffer zone sensors 14A, 14B are connected in the diagonally opposite arm of the bridge. The other two arms of the bridge have a resistor and a parallel combination of a variable resistor and a phase shifting capacitor. The bridge output is fed to an amplifier (24) Fig. 3 (not shown) the output of which is compared with a reference (26) the error activating a Schmitt trigger circuit (27) controlling a pair of relay contacts (29) in the heater circuit. The "thermal pivotal zone" may be adjusted by moving the buffer zone sensors 14A, 14B. The apparatus has particular application to a nuclear magnetic resonance spectrometer.