GB878053A - Temperature controlled oven for a frequency standard generator - Google Patents

Abstract

878,053. Automatic temperature control systems. AMPHENOL-BORG ELECTRONICS CORPORATION. Aug. 31, 1959, No. 29662/59. Class 38 (4). [Also in Group XIII] In an automatic temperaturecontrol system for a frequency standard generator, temperaturesensitive components of an oscillator are contained within an inner oven enclosed within an outer oven; each oven has a separate heating element and control circuit, and temperature-sensitive components of the inner oven control circuit are contained within the outer oven. As shown, a crystal 11, associated capacitor 13 and inductance 14 of an oscillator 10 are contained in an inner oven 12 heated by an element 16. A temperature-sensitive resistor 43 is connected as one arm of a bridge having in the remaining arms resistors 44-47. The out-ofbalance voltage of the bridge control the amplitude of oscillation of a transistor oscillator 60, the frequency of which is determined by a resonant circuit 59. A transistor amplifier 66 is coupled to the resonant circuit by a winding 65. A transformer having a primary 67 in the collector circuit of the transistor 66 has a secondary 68 supplying the temperature-sensitive bridge and a secondary 75 connected to a transistor amplifier 76. The voltage across a secondary 78 of a transformer in the output from the transistor oscillator 76 is rectified by a full-wave rectifier 80 and applied as a bias to the base of a transistor 83 controlling the current to the heating element 16. The element 16 is energized so as to tend to maintain the inner oven temperature constant at the turning-point of the crystal 11 by the output voltage of the oscillator 60 falling to zero as the temperature increases. The temperature of the outer oven is controlled by a temperaturesensitive resistor 89, through a modification of the system for the inner oven, varying the supply to a heating element 20. The output of a transistor oscillator 105 is fed to a transistor amplifier 108, the output of which is rectified to apply a bias to the base of a transistor 118 controlling the current to a relay coil 119. When a temperature-sensitive bridge comprising resistors 85-89, approaches balance the current to the relay coil 119 is reduced and a relay contact 122 is opened to disconnect the element 20 from a battery 121. The components comprising the inner oven controller 42 are contained in the space between the inner and outer oven.