Patent GB-1145010-A (GB)
Title: Improvements relating to the display of variables
Inventor: BET DONALD VICTOR
IPC: G06F3/153
Filed: 1967-10-06
Abstract: 1,145,010. Cathode-ray tube displays. NORTH AMERICAN AVIATION Inc. 6 Oct., 1967 [6 Feb., 1967], No. 45886/67. Heading H4. In a visual monitoring arrangement for a plurality of variables which may have normal or abnormal values, electrical signals representative of the variables are gated in groups of at least one to a cathode-ray display tube to produce a display which has one form when the variables have normal values and a different form when the variables have abnormal values and means are provided for determining, before the signals are supplied to the display tube, if a group contains an abnormal variable representative signal the means then operating on detection of such a signal for immediately gating the group containing this signal to the display means. As described, the variables, comprising four groups each of eight variables appertaining to operating parameters of an engine, are supplied to a buffer 13, Fig. 1, as 32 simultaneously effective normalized and linearized signals. At the output of 13 the signals are supplied to a processor logic circuit 2 and to a comparator logic circuit 3. The latter circuit includes a comparator 17, which may take the form described with reference to Fig. 8 (not shown), and which operates to produce an output signal when the input signal is higher-or-lower than predetermined limits, i.e. when it is abnormal. Thus, under the control of a counter 5 driven by a clock 20, circuit 3 operates when an abnormal variable is detected to produce an output from a logic circuit 12 which identifies that one of the four groups of eight variables in which the abnormal variable occurs. Simultaneously with this operation the processor logic circuit 2 operates under the control of a second clock 72, running at a much lower rate than clock 20, and a counter 4, to produce via a comparator 21 (which may be similar to comparator 17), a signal indicative of the occurrence of an abnormal value variable and via a horizontal sweep generator 9, a succession of sawtooth waves of amplitude proportional to the value of successive variables. The latter are utilized to produce the horizontal deflections of the beam of the display CRT 11, the vertical deflections of which are produced by a step waveform from a sweep generator on which the output of a sine wave generator is superimposed so that, in the absence of the detection of an abnormal variable, the display has the bar graph form shown in Fig. 2. When, however, the circuit 3 detects an abnormal value the output from logic circuit 12 operates via a control circuit 18 to set counter 4 immediately to the unit (= group) count in which the abnormal value occurred. The output from comparator 21 which occurs for each abnormal value in the eight variables forming the group then operates via a switch means 58 to inhibit the sine wave generator 30 so that the horizontal traces appertaining to the parameters having abnormal values take the form of a thin line as shown in Fig. 3 in respect of the pressure ratio and fuel flow of engine number 4.