Document Type and Number:
Japanese Patent JPS5118651
Kind Code:
B1
Abstract:
1,273,037. Resistance furnace. PERKINELMER CORP. 28 Aug., 1969 [7 July, 1969], No. 42946/69. Heading H5H. [Also in Division G3] A furnace, particularly for subjecting a sample to programmed temperature variations, comprises a resistive heating element and temperature sensor 32 with a non-linear temperature coefficient of resistance connected in parallel with a resistive element 36 whose temperature coefficient of resistance is substantially zero, so that in use the combined resistance temperature coefficient of the heating element 32 and resistive element 36 is more linear than that of the element 32 alone, and the resistive element 36 is also arranged to heat the furnace. As shown, a nickel heating foil 32 is formed by conventional printed circuit techniques on an insulating support 34 which is bent around the aluminium shell 12 of the furnace and a nickel-chrome resistive foil 36 is likewise formed on insulating support 40, and wrapped around the heating foil, the foils 36, 34 being secured by a metal clip 38 insulated from foil 36 by insulating material 40. The furnace may be used in various analytical apparatus e.g. a scanning calorimeter, a thermal gravimetric analysis instrument or a thermomechanical analysis instrument as shown. The heating element 32 and resistive element 36 are energized via a thyristor whose firing angle is controlled. Such control is effected by measuring the impedance of the temperature responsive parallel arrangement 32, 36 by making the arrangement part of a potential divider. A set point signal is provided by a second potential divider supplied by a D.C. source whose amplitude may be varied in accordance with the desired temperature programme. A chopper alternately connects the set point signal and the signal representing furnace temperature to a capacitor. The voltage from the capacitor is applied to an amplifier to produce an alternating voltage representative of the difference between the set point voltage and the voltage across 32, 36. This signal is applied via a D.C. amplifier to the S.C.R. trigger control circuit which effects an amplitude to phase conversion for controlling the angle of the S.C.R. and hence the furnace temperature.
Application Number:
JP6709469A
Publication Date:
June 11, 1976
Filing Date:
August 25, 1969
Export Citation:
International Classes:
F27D11/02; G01K1/14; H05B3/00; G05D23/24; (IPC1-7): H05B1/02; F27D11/02; G05D23/19