GB1501067A - Indicator arrangement - Google Patents

Abstract

1501067 Indicator arrangement SIEMENS AG 30 July 1976 [5 Aug 1975] 31995/76 Heading G4H [Also in Division G3] An indicator arrangement comprises a display 9<SP>1</SP> (e.g. lamps) for a control circuit to be monitored; a circuit for presenting a desired value S for the control circuit in digital form and including output circuitry 6<SP>1</SP> which provides different combinations of digital output signals according as the magnitude of S lies above, below or within a predetermined interval (A, B); and an evaluator circuit 7<SP>1</SP> receiving both the digital output signals and a further signal 701<SP>1</SP> which is representative of a present state of the circuit 7<SP>1</SP> feeding a switching signal 702<SP>1</SP> to the display which is such as to switch it on or off if S lies above or below (A, B) and which leaves it in its present state if S lies within (A, B). The size of the interval is chosen so as to prevent unnecessary flicker of the display. As described, the arrangement is used for brightness control of projector lamps, the desired value S being obtained from a control circuit 4, Fig. 1 (not shown), which receives, inter alia, intensity values via a sensor (1) a core store (1) and a D/A converter (3). The desired value is used to control thyristor regulators in a power unit. As described, n values are monitored using n lamps in a multiplex cycle, a core store 8<SP>1</SP> (which may form part of store (1)) holding the n values of the present cycle for application to circuit 7<SP>1</SP>. Circuit 6<SP>1</SP> may be formed from operational amplifiers, actuated when S>A and S>B, together with Schmitt triggers, an inverter receiving one amplifier output and an AND gate receiving the inverted output and the other amplifier output. Fig. 4 shows the operation of circuit 7<SP>1</SP>. Figs. 1 and 3 (not shown) illustrate logic circuitry 7<SP>1</SP> using five bits from the 8-bit output of an A/D converter. Separate circuitry may be provided for each lamp, in which case store 8<SP>1</SP> is not required. An additional switch in the input to circuit 6<SP>1</SP> allows other quantities of interest to be displayed.