GB989636A - Improvements in and relating to peak signal storage systems - Google Patents

Abstract

989, 636. Peak voltage measurement; gas chromatography; phase sequence determinations. UNION CARBIDE CORPORATION. Nov. 10, 1961 [Nov. 25, 1960; Dec. 6, 1960], No. 40259/61. Headings G1N and G1U. A signal processing system for determining and storing the peak magnitude of each of a recurring number of repetitive first electrical signals having varying amplitudes occurring at fixed predetermined times comprises a signal store 10 mechanically adjustable to develop and store a second electrical signal which is fed with the corresponding first signal to an amplifier 5 which detects and amplifies the difference in magnitude and direction between the first and second signals, a motor 8 connected to the output of the amplifier mechanically connected to adjust the store in a direction which will reduce the difference between the first and second electrical signals, a phase detector connected to the output of the amplifier which will produce an output when the second signal exceeds the first and a switch operated by the output of the phase detector for interrupting the power to the motor upon an output therefrom. The system may be used in association with gas chromatographic analysis apparatus in order to store peak output signals from the analyser, and subsequently provide a summation signal representing the algebraic sum of these outputs. In the embodiment of Fig. 1 the signal store 10 consists of a potentiometer, one such potentiometer being required for each component in the analysis (13 is another such potentiometer). The input signals from the analyser are fed via programmed timer switches 20, to channel switches 15, 16 (corresponding to the number of signals in the analysis) and also to a recording device 1, which is coupled to the retransmitting potentiometer 4. The channel switch actuates a relay 9 and thus establishes the servo loop containing the potentiometers 4 and 10, the servo amplifier 5 and the motor 8. The servo action causes the wiper of the potentiometer 10 to follow that of the potentiometer 4 when this represents an increasing input. The output of the servo amplifier is also connected to a phase sensitive detector, which may be of the form shown in Fig. 4. When a gas component signal is increasing in magnitude, the input to the servo amplifier is negative, and this causes output voltages e 4 , e 6 taken from a centre tapped transformer whose outer tap is fed from a reference voltage e 5 to be such that a current flows in the lower loop of the detector shown, so that the net output to the grid of the thyratron shown is positive. The thyratron, which is normally fired, thus remains so. If however the servo amplifier output had been positive, representing a decreasing input signal, the thyratron would be switched off, causing relay 24 to open. When this occurs a carrier lead connecting all the servos together is broken and the movement of the shaft of the storage potentiometer is halted. Provision is made for the signals stored to be transferred to a computer, after which the stores may be reset to await the next peak. Circuitry is also indicated for deriving the sum of the signals from the various storage potentiometers.