Abstract:
As the complexity of industrial processes has incr**ssd, there has been a consequent increase in the number of process variables (such as temperature, pressure, flow, pH) to be controlled # and it has bene increasingly evident that further development would be difficult or even impossible without the aid of devices which would automatically measure and control at least some of these process vesiables. Automatic control does not replace the human operator but rather supplenents him. Automatic control of at least some of the process variables allows him to concentrate upon the parts of the process which r4quire his special skill. Zn the absence of instruments which directly measure and control the quality of product, it is necessary to control variables such as temperature,, pressure,, pH etc., at values which experience has shown result In the greatest safety of the operator and the highest qullity and quantity of product.
