PID


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PID

PID

(1) (Process IDentifier) A temporary number assigned by the operating system to a process or service.

(2) (Proportional-Integral-Derivative) The most common control methodology in process control. It is a continuous feedback loop that keeps the process flowing normally by taking corrective action whenever there is any deviation from the desired value ("setpoint") of the process variable (rate of flow, temperature, voltage, etc.). An "error" occurs when an operator manually changes the setpoint or when an event (valve opened, closed, etc.) or a disturbance changes the load, thus causing a change in the process variable.

The PID controller receives signals from sensors and computes corrective action to the actuators from a computation based on the error (proportional), the sum of all previous errors (integral) and the rate of change of the error (derivative). See PAC.


Inputs from a PID
The large white boxes are Opto 22 SNAP PACs, which are programmable automation controllers that are processing the PID loops in Chevron's research facility in Richmond, Virginia. The wires come from thermocouples that sense pipe temperature in a laboratory test that analyzes the best way to break down crude oil. The PACs determine when to raise and lower the temperature, and the three modules with the black sockets send digital signals to the heaters (cables not connected in this image). (Image courtesy of Opto 22, www.opto22.com)
References in periodicals archive ?
The results show that a better control effect can be obtained with fuzzy PID control, the tracking accuracy is higher and the delay time is shorter compared with traditional PID control.
Adding moxifloxacin to routine, empiric treatment for acute PID would be an especially tough call if it also meant dropping doxycycline, a drug that is otherwise attractive because of its low cost and broad spectrum of activity against other PID pathogens.
Computation of stabilizing PI and PID controllers by using Kronecker summation method.
The response of the gas turbine plant with the PID controller compared with the open loop response is shown in Figure 3.
There is little debate about how IUD insertion increases risk of PID in the period immediately following the procedure.
Tim Green, a Coat|Rose attorney, says, "In certain instances cities prefer the infrastructure to be financed through the PID rather than a traditional MUD, because the City prefers more direct control over the financing, the assessment is fixed up-front, or because of the reduced overhead in using a PID instead of a MUD.
He also hoped that the PID will also play constructive role in upcoming general elections.
Also, by evaluating the relationship between the timing of testing for gonorrhea and chlamydia (GC/CT) and the risk of developing PID within 90 days after IUD insertion, the study fills a large gap in the evidence base for the optimal timing and necessity of testing women who have no symptoms of gonorrhea and chlamydia.
Dennis She, President and CEO of ET Solar, commented: "We are very proud that our modules have passed the PID test.
Ureaplasma parvum (UP), however, was not associated with PID in a substudy of women participating in the PEACH (PID Evaluation and Clinical Health) study.
PID control is widely adopted in many fields because of its simple structure, high reliability and easily implementation.