Digital processing process control loop using computer

In a digital computer-control system, the feedback controller has a pulse transfer function. What we need is an equation or algorithm that can be programmed into the digital computer. At the sampling time for a given loop, the computer looks at the current process output x, compares it to a setpoint, and calculates a current value of the error. This error, plus some old values of the error and old values of the controller output or manipulated variable that have been stored in computer memory, are then used to calculate a new value of the controller output m,. 

A modern commercial mass spectrometer will incorporate a computer or will offer a facility to communicate with a computer via a data link, for example, to a plant control system using serial, ethernet or analog, and/or digital signals. This allows data to be stored and manipulated, often in real-time , so that results can be displayed to the user in a convenient form or to be utilized for process control either automatically via a closed loop or for operator fine-tuning . A mass spectrum may be displayed as a continuous scan over a specified mass range similar to a strip-chart, but this is difficult to interpret, and is not directly quantitative. 

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