Process variable

About: Process variable is a research topic. Over the lifetime, 3983 publications have been published within this topic receiving 43130 citations. The topic is also known as: process parameter.

Electronic controller for valve actuators

Abstract: An electronic controller is provided to control the energization of an electrical actuator to readjust a valve which controls the flow of a fluid in a controllable process. The controller is responsive to two signals, one of which is produced by a process sensor to represent the instantaneous magnitude of a predetermined process parameter and the second of which constitutes a set signal representative of a desired magnitude of the parameter. The signals are compared, and the sense of any resulting error signal is used to control the direction of movement of the actuator while the instantaneous magnitude of the error signal, during a succession of equal time intervals, is used to control the rate of movement of the actuator by controlling the extent of movement of the actuator during each of the time intervals. The actuator is jointly responsive to these two controls and moves in a series of incremental steps, the sizes of which decrease exponentially to match the process loop variable's exponential change with time, as the error signal reduces to zero.

Method of digital process variable transmitter calibration and a process variable transmitter system utilizing the same

Abstract: A method of digital process variable transmitter calibration includes the steps of sensing the process variable (PV) to produce an analog output which is converted to a digital signal representation. The digital signal is corrected by a microprocessor using a characterization equation previously individually developed during a manufacturing testing of the process variable transmitter over a predetermined range of environmental stimuli to ascrtain the coefficients for a polynomial in the form of PV=Ao =A1 P+A2 +. . . Ai Pi. Thus, the digital computer produces a process variable representation as a modified digital output. Subsequently, the digital output from the computer is converted to a conventional 4-20 mA analog signal for use as a process control signal. The process variable transmitter apparatus utilizing the aforesaid method includes means for receiving an output from a process variable sensor, an analog-to-digital converter for converting the received output from the sensor to a digital representation, a digital computer, a non-volatile memory for storing an individualized correction equation determined during the manufacturing testing of the transmitter and a digital-to-analog converter for converting the computer output to an analog control signal.

Statistical methods for the estimation of process variation effects on circuit operation

Abstract: In this paper, a technology computer-aided design (TCAD) driven method for accurate prediction of the performance spread of integrated circuits due to process variations is presented. The methodology starts with the development of the nominal process recipe and process simulators are calibrated to an existing process to obtain nominal device characteristics. After determining nominal process parameters, their variations are introduced followed by screening experiments to determine the relative effects of given process variations on the input-output delay and the average power dissipation in a circuit. Response surface models (RSMs) are then generated based on critical process factors identified. Process parameter optimization is performed using these RSM models to tune the mean circuit performance and to improve the yield. This methodology is demonstrated on a 33-stage ring oscillator manufactured with a CMOS design flow. The proposed methodology maps the process domain to design space, and plays a key role in design for manufacturability (DFM) to quantify direct impact of the process variations on circuits.