Patent GB-799825-A (GB)
Title: Improvements in or relating to apparatus for determining the frequency of electrical signals
Inventor: WALLS WALTER RICHARD
IPC: H03K23/82
Filed: 1955-02-22
Abstract: 799,825. Frequency measurement. RANK CINTEL, Ltd., [formerly CINEMA-TELEVISION, Ltd.]. Feb. 22, 1956 [Feb. 22, 1955], No. 5261/55. Class 37. Apparatus determining the frequency of a periodic signal comprises a time-controlled gate repetitively applying the signal for a predetermined time interval to a pulse counting chain in which a first element counts on a binary scale and subsequent elements count on a denary scale; the first element operating to pulse the second element each time the number of cycles received by the counting chain input becomes a multiple of the scaling factor of the first element, and the predetermined time interval being a multiple of one second by a factor equal to a multiple or submultiple of the said scaling factor; the counts of the successive elements being displayed decimally to indicate the value of the input frequency. A periodic electrical signal is applied (Fig. 1) to a known gating circuit 2 controlled by timing device 3 for application to a 4-stage binary counter 4 for a period of 1 second multiplied by <SP>1</SP>/ 10  the scaling factor of the counter, i.e. 1.6; the counter being provided with a display 5 registering the pulses arriving over the time period and delivering an output pulse, whenever the number of received pulses becomes a multiple of the counter scaling factor, to a decimal counter 6 registering its count on display 7 as <SP>1</SP>/ 10  the input frequency and delivering an output pulse to a further decimal counter (not shown) on completion of each decade. Displays 5, 7 may comprise neon lamps indicating the states of the respective binary and decimal counter stages, or decimal counter operated direct reading meters of the kind described in Specifications 572,884 and 735,942, [both in Group XIX], in conjunction with a meter display. Binary counter 4 (Fig. 2) comprises triodes 15, 16 having a common high value cathode resistor 19, separate anode resistors 13, 14 fed through a common resistor 12, and parallel R.C. circuits 17, 18 interconnecting opposite grids and anodes so that initially one valve conducts and one is cut off. Arrival of each negative signal pulse at the junction of resistors 12, 13, 14 cuts off the conducting valve and renders the opposite valve conducting, so that every second input pulse generates a pulse at the anode of triode 15 which turns over a second similar triode circuit, which in turn triggers third and fourth similar circuits in sequence to deliver to the succeeding decade counters over terminal 32 a pulse for every 16 input pulses. Pairs of equal resistances 22, 23; 24, 25; 26, 27; and 28, 29 related in the proportions 8 : 4 : 2 : 1 connect the anodes of the pairs of counting triodes to the respective terminals of a centre zero microammeter 30 shunted by variable scaling resistance 31. At zero count the meter is fully deflected negatively and as the count progresses its pointer moves positively in steps until it is fully deflected positively at a count of nine ; the meter pointer taking up sixteen distinct scale positions calibrated (Fig. 3) to represent frequencies of 0, 0.6, 1.2, 1.8, 2.4, 3, 3.6, 4.2, 4.8, 5.4, 6, 6.6, 7.2, 7.8, 8.4 and 9 times any decimal multiplier, in addition to the integral calibration of 1 to 9.