Patent GB-1255396-A (GB)
Title: Method and device for measuring the slope of a pulse leading edge
Inventor: MAX JACQUES
IPC: A61B5/00
Filed: 1969-02-20
Abstract: 1,255,396. Measuring pulse slope. COMMISSARIAT A L'ENERGIE ATOMIQUE. Feb.20, 1969 [March 1, 1968], No.9147/69. Heading G1U. In a method of measuring the slope of the leading edge of a triangular electric pulse consituting part of a signal which may be accompanied by high background noise, a sawtooth signal having a known constant slope is generated to commence at the beginning of the pulse, and the amplitude of the pulse at a given instant is divided by the amplitude of the sawtooth signal at the same instant, the resulting magnitude being proportional to the required slope. It is shown in the Specification that such magnitude represents the required slope with the virtual elimination of the effect of noise. The method is used in a system for analysing the pulses derived in studying nystagmic jerks of the eyeball. The pulses are obtained from periorbital cutaneous electrodes applied to a patient subjected to a periodic pendular motion, and each pulse has a slow edge of small slope and a fast return edge. It is required to measure the slope of each slow edge, the mean slope and the number of pulses in a given period. When the direction of oscillation of the patient reverses, the pulses are first extinguished and then reappear in the opposite polarity (curve A) Fig. 1. The pulses are applied to the input 10, Fig. 2, of the slope measuring circuit, which leads to two inhibition circuits 12, 121 having differentiators 14, 14<SP>1</SP> for fast positive and negative returns respectively. The differentiator outputs are shaped at 20, 20<SP>1</SP> and passed via OR gate 22 to trigger the sawtooth generator 34, which is consequently triggered following each fast return. The pulses also pass to respective measurement permission circuits 24, 24<SP>1</SP> (shown in detail in Fig. 5) which provide respective output pulses, of fixed width # on line 26, 26<SP>1</SP> and respective signals on line 30, 301 commencing at the second received pulse and of width corresponding to the time difference between consecutive pulses + the fixed time #2 1 . This signal is applied to the differentiator in the opposite line to inhibit its operation. This prevents confusion between e.g. the fast edge of pulses of one polarity and the slow edge of pulses of opposite polarity. The input at 10 is also applied to a base line correction circuit 32, wherein each trigger signal from the gate 22, corresponding to a fast pulse causes the signal level from the circuit 32 to be returned to zero. The base line corrected pulses are applied to a divider circuit 36 together with the signal from the sawtooth generator 34. The output from the divider represents the required slope and is passed to a recorder 44. The output will be in the form of pulses corresponding to each nystagmic pulse, each having an amplitude corresponding to the slope of the related pulse. The pulses are also passed via a line 48 to a circuit for counting them and determining their mean level, Fig.3 (not shown). The trailing edges of the pulses are differentiated (52), to provide an output which controls a monostable multi-vibrator (54) to provide a fixed width sampling pulse which is applied to an extraction circuit (56). This receives at its other input the signal input pulse delayed through delay line (50), and provides output pulses of fixed width, and amplitude related to individual slopes. These are integrated (60) and the resultant passed to a divider (68). The other input of this receives an analogue voltage corresponding to the number of pulses making up the integrated value, derived by counting (at 64) the pulse outputs from the differentiator (52), and passing the count value through a D-A decoder (66). The divider output is passed to a two channel recorder, which also receives the count value directly. Measurement permission circuit, Fig. 5 (not shown). The purpose of this circuit is to provide an output when differentiated signals representing the fast returns of nystagmic pulses of one polarity are detected close together, the output being used to inhibit the differentiator for the fast returns of pulses of the other polarity, so that this cannot erroneously respond to slow edge signals of the first polarity. The differentiator signals, after passing through a shaping circuit (20) are applied to an FET gate (82) which opens to apply positive potential to the base of a normally conducting transistor (94) in a monostable (80), thereby cutting it off. The output potential at the collector of the other transistor of the monostable (92) rises. If the next pulse appears within the relaxation time of the monostable, the monostable capacitor is recharged by current flow through a resistor (98) and a positive blip appears on the signal on the output line (27). The output (on line 27) is passed to two circuits (84, 86), one of which (84) shapes and inverts the output pulse to remove the blips, and passes it to a logic circuit (90). The other circuit (86) is a trigger circuit which is caused to produce pulses in response to the blips. These are amplified and shaped (at 88) and passed to the other input of the logic stage (90). The first such pulse, corresponding to the second nystagmic pulse, sets the logic stage (90) to produce an output which continues until the stage is reset by the ending of the pulse from the shaping circuit (84) following the end of the series of nystagmic pulses and the return of the monostable to its normal condition. The output on the line 30 is applied to inhibit the other differentiator (12 or 12<SP>1</SP>), Fig.2.