GB635186A - Instrument for measuring or indicating the characteristics of electric pulses - Google Patents

Abstract

635,186. Thermionic valve ammeters and voltmeters; frequency measurements; combinations of instruments. LORD, A. V., LAX, L., and PYE, Ltd. March 3, 1948, No. 6651. [Class 37] An instrument for measuring or indicating the characteristics of the pulses of a train of electric pulses comprises two movable pointers 6, 13, Fig. 2, which overlap one another, one pointer 6 indicating the duty cycle against one calibrated scale 15, the other 13 indicating the pulse repetition frequency against a second calibrated scale 16, and the crossing point p of the two pointers indicating the pulse width against a third set of calibrations 14. The train of pulses is fed through a limiter 1, Fig. 1, for limiting the pulses to a constant amplitude, and thence to two parallel circuits of which the first includes a valve 2. The pulses are applied with positive sign to the grid of this valve through a condenser-resistance network 3, 4 having a long time constant. A battery 5 biasses the grid negatively to such a value that the valve is non-conducting between pulses so that the anode current is proportional to the duty cycle, i.e. the ratio of the time duration of the pulse to the interval between the leading edges of two successive pulses. The anode current is passed through a meter, the pointer 6 of which indicates on the " duty cycle " scale 15, Fig. 2. The second of the two parallel circuits comprises an oscillator consisting of a valve 7 and feedback transformer 8. The pulses are fed to the grid of this oscillator via a condenser 9 and resistance 10 so that the valve oscillates in synchronism with the pulse train. The output of the valve 7 is fed via an integrating circuit consisting of a condenser 11 and resistance 12 to a meter of which the pointer 13 moves over the scale 16, Fig. 2, calibrated in terms of pulse repetition frequency. The crossing point p of the pointers 6, 13 co-operates with a family of curves 14 on the instrument dial to indicate the pulse width, which is the ratio of the duty cycle to the pulse repetition frequency.