Combined analogue and digital display system - markes use of solid state indicators and alarms for process control purposes

摘要

The electronic indicating and monitoring system for chemical or other process is based on active and passive electronic elements for the transmission and display of data. The system provides the operator of the process with an accurate analogue reading with an indication of the direction of change and speed of change of any variable. The indication can be effected with symbols, marks or figures arranged on an arc of a circle or in linear form on or behind transparent scales. The display can use light-emitting diodes or liquid-crystal type of solid-state devices. Different colours can be employed to indicate upper and lower range limits or othe critical criteria. Limit indicators may be combined with electronic relays to provide an additional output signal to activate separate alarm systems.