Patent GB-1160890-A (GB)
Title: Monitoring and Control System
IPC: G08C25/04
Filed: 1966-09-29
Abstract: 1,160,890. Cathode-ray tube displays. MONSANTO CO. 29 Sept., 1966 [30 Sept., 1965] No. 43620/66. Heading H4T. In a process control and monitoring system a signal display representative of the values of a number of different parameters at each of a plurality of monitored stations is presented in sequence at a like plurality of different respective positions on the screen of a cathode-ray display tube and means are provided for controlling the values of the parameters at the particular stations. Although of general application the particular process considered is the control and monitoring of fluid flow in a plurality of pipes utilizing a system in which signals (P) (Fig. 1) from transducers responsive to the rate of fluid flow ("process variables") in such pipes are compared with signals (SP) indicative of the desired rate of flow ("set point") and the difference utilized to provide a control voltage signal V ("valve position") for varying the opening of a valve controlling such flow. Fig. 2a shows one form of display for the P, SP and V parameters in the case of monitoring the flow in a number of pipes F1 . . . F9 in which the set point SP is indicated by horizontal line 52 (generated either electronically or painted on the tube face) with the length of each vertical line, each of which moves up or down in accordance with its own set point, representative of the maximum flow rate for each pipe, the short horizontal lines representative of the actual flow rate P and the bright dots representative of the extent of opening of the flow control valvethe V signal. Thus the distance of the short horizontal lines from line 52 is indicative of the percentage departure of the P signal from the (desired) SP signal and the distance of the bright dots from the lower end of the vertical lines is indicative of the percentage of full opening of the flow valve-the V signal. In a variation of this display only the traces showing some error in the process, e.g. F5 and F8 are displayed the remaining no error traces being blanked-out (Fig. 2e, not shown). The display may be modified by having all the vertical lines at the same height with the SP signal indicated by electronically generated circles intersecting such lines and the P signals indicated by bright dots on each line (Fig. 5a, not shown). In another arrangement in which the vertical positions of the lines are determined by the SP signal each line is provided with two spaced bright dots which indicate the limits between which the P signal should lie and departure from such limits may be made more identifiable by intensification or by flashing of the line(s) concerned (Fig. 5b, not shown). Provision is made for automatic control of the flow rate by comparing the P signal with the SP signal in a controller 26 (Fig. 1) and employing the result of such comparison to vary the opening of the flow valve 20. Alternatively, with switch 32 in position 30 the valve may be controlled manually by adjustment of resistor 31. A facility comprising a light-gun which is directed at the display corresponding to a predetermined station allows the SP and V signals to be adjusted to desired values and selectively controls digital display means displaying either the SP, P or V signals. A three-colour display tube may be employed and the colours utilized to indicate normal operation, fault conditions and operation in the manual control mode, Fig. 9 (not shown). Fig. 3 shows the general scheme in which the P and V signals are supplied via an input system 60 to means 62 which generates the beam deflection and intensity control signals controlling the production of the visual display of the various parameters at the different stations and controls selectively, in accordance with the operation of light-gun 72, the generation of the SP and V signals for the various stations and the digital display on means 70. Additionally, an auxiliary display 66 which may be either a strip chart or an oscilloscope is included to provide a trend display. The means 62 may be associated with a digital computer. The Specification describes both digital and analogue arrangements for the production of the beam deflection and intensity control signals and for the production of the SP, and V signals together with alternative arrangements for controlling the digital display. The deflection and intensity control signals have the form shown in Fig. 4 in which, considering the display of Fig. 2a, the vertical deflections are produced by a sawtooth A modified in absolute amplitude by the SP signal-pulse train B-to provide the Y axis deflection waveform, the horizontal deflections by a stepped waveform applied to the X axis and the beam intensity (Z axis) by rectangular pulses of duration slightly less than that of the sawtooth A. For the production of the short horizontal lines representative of the P signals short duration pulses are superimposed on the X axis waveform and for the production of the bright dots representative of the V signals short duration pulses are superimposed on the Z axis waveform both of these short duration pulses also being utilized, in the case of the digital arrangement for the waveform generation, to arrest, momentarily, the rise of the sawtooth producing the Y deflection so that an enhanced display is produced. If desired, a particular display such as F2 may be made to "stand-out" by increasing the amplitude of the respective beam brightening pulse.