Patent GB-638026-A (GB)
Title: Improvements in or relating to pulse analysers
IPC: G01R29/02
Filed: 1947-06-14
Abstract: 638,026. Pulse discriminator circuits. POOLE, M. J. June 14, 1947, No. 15706. [Class 40 (vi)] In a pulse analyzer input pulses of differing amplitudes produce short uniform output pulses coincident with the peaks of the input pulses and these output pulses are distributed among a plurality of output circuits in dependence upon the amplitudes of the input pulses. General operation. Incoming pulses of differing voltages are applied to amplitude discriminators D1 ... D4, Fig. 2, having graded back biassing and operating to voltages of, say, 0.5, 10 or 15 volts respectively. Each discriminator when operated applies a positive priming pulse to a following gate circuit and a negative blocking pulse to a preceding gate circuit. Thus a pulse of 13 volts will operate discriminators D1, D2 and D3 but not D4, thus blocking gate circuits G1 and G2 while opening G3. The incoming pulse train is also applied to a pulse generator T from which is derived a train of pulses, coincident with the incoming pulses but of equal amplitudes and short duration, which are applied to each gate circuit G1 ... G4. The open gate G3 is therefore triggered and transmits a pulse to an associated counter C3 at a time theoretically coincident with the input pulse but in practice delayed by approximately 1 micro-sec. This delay allows the slowly rising input pulse to operate the appropriate number of discriminators before the desired pulse arrives to trigger the open gate. Circuit details, Fig. 5. The incoming pulses are inverted and applied at X to the discriminators D1 &c. which each comprise a modified Schmitt trigger circuit such as V14, V 15. The anode of V14 is coupled to the grid of V15 by resistor R16 and there is a common cathode resistor R14. The additional condenser C16 increases the speed of triggering and it is stated that the condenser C14 increases the initial steepness of the output pulse. To increase the stability of the voltage at which a discriminator fires the bias resistors R15, R16, R17 are wire-wound. When the incoming pulse has a voltage sufficient to trigger a particular discriminator the valve V15, V19, &c. conducts and the resultant negative anode pulse is inverted at V16, V20, &c. to produce a positive pulse on the screen grid of the following gating valve V17, V21, &c. The negative pulse is also applied directly as a blocking bias to the suppressor grid of the preceding gate valve. Only the gate valve following the last discriminator which is triggered is therefore conditioned to conduct, conduction being prevented however by a large negative bias on the control grid. The incoming pulses a, Fig. 4, are applied also to the pulse generator unit T, an amplifier V6 of which removes the negative tail. The cathode pulse b is differentiated by the network C6, R6, the resulting pulse c being amplified and inverted by V7, and further amplified and inverted and also limited by V8. The resultant pulse e operates a Schmitt trigger circuit V9, V10, the output pulse f of which is differentiated (g) and amplified by V11. The final output pulse h is taken from a cathode follower arrangement V12, V13, and applied as positive bias to the control grids of all the gating valves V17, V21, &c., the previously conditioned one of which conducts. The consequent anode pulse operates a counting circuit (not shown). A group discriminator GD may be employed to first select a portion of the total input voltage range for analysis. The input pulses are then applied to an amplifier V1 which has a negative bias adjustable between 0 and 100 volts. The excess of input voltage over bias is amplified and inverted and limited to 25 volts by V2. V3 then amplifies the output and the final output pulse is taken from the anode and cathode of a cathode follower arrangement V4, V5 and applied at X to the discriminators Dl &c.