Abstract: A gas chromatograph for connection to a source of carrier gas and a source of a sample gas. The gas chromatograph includes a first bridge circuit with a sample sensor connected therein and a second bridge circuit with a reference sensor connected therein. The outputs of the bridge circuits are digitized and then subtracted from each other in a processor.

Abstract: The present invention is directed to a gas chromatograph having a display screen. The gas chromatograph includes an explosion-proof housing and a transparent panel secured to the housing. The display screen is disposed in the housing and is visible through the transparent panel. A gas chromatograph (GC) assembly is disposed in the housing and includes a column for separating components of the gas and a detector for detecting the components of the gas. An electronics assembly is disposed in the housing and includes a microprocessor and memory. A graphical user interface (GUI) software application is stored in the memory and is executable by the microprocessor to display a plurality of windows on the display screen. The windows contain information about the operation of the gas chromatograph.

Abstract: The present invention is directed to a gas chromatograph (GC) module having a column assembly and a printed circuit board mounted to a valve assembly. A plurality of electronic devices are mounted to the circuit board. The electronic devices include non-volatile memory, pressure sensors and detector devices.

Abstract: A process control system is provided in which a process variable is compared to a set point for the process variable by a process controller with the results of the comparison being utilized to control the process in such a manner that the process variable will be substantially equal to the set point for the process variable. A critically damped response of the process variable to a change in the set point is achieved by utilizing a process controller which has the characteristics of a proportional-integral-derivative controller followed by a first order lag. Tuning of the process controller is accomplished by changing a time constant which is common to the proportional, integral and derivative terms of the proportional-integral-derivative controller and also common to the first order lag.

Abstract: In the measurement of a variable process parameter and control of the process in response thereto, a transform of a process parameter measurement signal that can be described as the time derivative of a second order or higher lagged process parameter measurement signal is utilized to provide predictive capability. This transform is combined with the output of a PI controller to the input of which the process parameter measurement signal has been fed, thereby generating a process variable signal that either directly or after passing through another controller is utilized as a process control signal for controlling the process in response to the measured parameter. The system is particularly well adapted to control of a non-self-regulating process.

Abstract: In the measurement of a variable process parameter and control of the process in response thereto, the time derivative of a second order or higher lagged process measurement signal is utilized to provide predictive capability in generating a process variable signal, in generating a process control signal, and in controlling the process in response to the measured parameter. The system is particularly well adapted to control of a non-self-regulating process.