Electrical measuring and control apparatus and a glass press embodying the same

Claim 1

IN AN APPARATUS FOR IRRADIATING, WITH AN ELECTRICAL WAVE OF A FIRST FREQUENCY PROPAGATED BY AN ENERGY RADIATING MEANS, AN OBJECT WHOSE ABSORPTION OF ENERGY FROM SAID RADIATING MEANS IS A FUNCTION OF TWO UNKNOWN QUANTITIES, AND FOR MEASURING VARIATIONS IN ONE OF SAID QUANTITIES: ENERGY RADIATING MEANS, A NETWORK IN WHICH SAID ENERGY RADIATING MEANS COMPRISES ONE ELEMENT, A SIGNAL GENERATOR PROVIDING A REFERENCE VOLTAGE AT SAID FIRST FREQUENCY COUPLED TO SAID NETWORK, THE OUTPUT OF SAID NETWORK COMPRISING AN ERROR SIGNAL VARIATIONS IN WHICH ARE REPRESENTIVE OF VARIATIONS IN THE ENERGY ABSORPTION OF SAID OBJECT, MEANS FOR VARYING THE OTHER OF SAID QUANTITIES AT A SECOND FREQUENCY TO MODULATE SAID ERROR SIGNAL AT SAID SECOND FREQUENCY, A PHASE SHIFTER COUPLED TO SAID SIGNAL GENERATOR AND HAVING AN OUTPUT COMPRISING A PHASE-SHIFTED REFERENCE VOLTAGE, MEANS APPLYING SAID PHASE-SHIFTED REFERENCE VOLTAGE AND SAID MODULATED ERROR SIGNAL TO A FIRST PHASE DETECTOR ADAPTED TO PROVIDE AN OUTPUT VOLTAGE HAVING A DIRECT CURRENT COMPONENT AND AN ALTERNATING CURRENT COMPONENT OF SAID SECOND FREQUENCY, THE DIRECT CURRENT COMPONENT OF WHICH IS A FUNCTION OF THE AMPLITUDE OF THE FIRST FREQUENCY COMPONENT OF SAID MODULATED ERROR SIGNAL THAT IS IN PHASE WITH SAID PHASE-SHIFTED REFERENCE VOLTAGE AND THE AMPLITUDE OF THE SECOND FREQUENCY ALTER-