Process control is a way for automated factories to operate their machinery from a central control room, generally resulting in fewer workers being needed to keep things running. It is used by engineers to maintain targeted output levels for variables such as voltage and the rate of production on working machines. Digital process control is process control that uses computers to monitor machines and environmental conditions on the manufacturing line. The different types of digital process control are batch control, continuous control, discrete control and statistical process control.
Batch digital processing control is achieved by combining raw materials in certain quantities, sometimes by heating or gluing them together. Pharmaceutical factories use batch control to synthesize chemicals and mix them to create medicines. Food manufacturing plants use batch control to ensure that the quality of a food product is the same each time it is made.
Continuous digital processing control deals with monitoring and controlling a process so it is always running. Uninterrupted manufacturing processes may include maintaining a constant water temperature in a water boiler or monitoring for the presence of combustible gasses in the atmosphere. As a way of ensuring workplace safety, manufacturing plants that create petroleum products, such as plastics and fuels, utilize sensors to monitor the flammable — and sometimes fatally explosive — hydrocarbon gases that are naturally emitted by the petroleum.
Discrete digital process control is used to monitor and run assembly lines that utilize robotic arms. Automotive manufacturing plants have robots that assemble car frames and spray-paint the bodies. Metal factories may have machines that create stamped or formed metals. Other manufacturing plants utilize discrete control to monitor machines that package food products.
Statistical digital process control is used to monitor how efficiently a machine is working. Data used to create statistics are compiled by sensors connected to a process control transmitter. The transmitter sends the data to computers that display the information in a series of graphs or control charts. The charts are used by engineers and other factory workers to determine whether there has been any fluctuation during the production process that may cause defects in the finished product. This allows workers to detect the presence of potential problems and work to correct them.
Digital process control is done with computers and sensors called data indicators. Data indicators may be designed to display the amount of voltage a machine uses, the levels or humidity present in the air, temperature levels, a system's gas or water pressure, and electrical current or voltage. Two common types of digital process control data indicators are water flow meters and thermostats. Water flow meters are sensors that test the temperature and the speed of water as it moves through plumbing. Thermostats measure the temperature of a substance and control a heating valve to raise or lower the temperature to maintain a set temperature.