Even as far back when compressed air was generated by bellows in a blacksmith shop there has always been the need for control. Too much air and the furnace was too hot, too little and the flame would be too cool, and very quickly the operator tired of the job of adjusting things manually.
Hence the invention of automatic controls for compressed air, starting as simple as mechanical/pneumatic means, and progressing to simple electrical controls using mercury switches. These days, with the easy availability of low cost and accurate sensing instruments, and many inexpensive data collection devices, the control and monitoring of a compressed air system is getting very sophisticated. This article discusses some old and new methods to monitor and control compressed air systems.