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3: Sensors and Actuators

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    • 3.1: Control Systems - Measurement Devices
      The most common control type used today in industry is a PID controller (proportional, integral, derivative), which allows the operator to apply different control techniques that can be used to achieve different settings in an experiment or process. A PID controller can be used in two main control mechanisms that include feed back and feed forward. The purpose of this article is to provide examples of common industrial control systems that apply different control architectures.
    • 3.2: Temperature Sensors
      Temperature sensors are vital to a variety of everyday products. Temperature control also has applications in chemical engineering. Examples of this include maintaining the temperature of a chemical reactor at the ideal set-point, monitoring the temperature of a possible runaway reaction to ensure the safety of employees, and maintaining the temperature of streams released to the environment to minimize harmful environmental impact.
    • 3.3: Pressure Sensors
      Pressure must be considered when designing many chemical processes. There are various types of pressure sensors that are available in the market today for use in industry. Each functions best in a certain type of situation.
    • 3.4: Level Sensors
      Level sensors allow for the level control of fluid in a vessel. Examples of where these sensors are installed include reactors, distillation columns, evaporators, mixing tanks, etc. Level sensors provide operators with three important data for control: (1) the amount of materials available for processing, (2) the amount of products in storage, (3) the operating condition. Installing the correct level sensor ensures the safety of the operator and the surrounding environment.
    • 3.5: Flow Sensors
      Flow measurement proves crucial in various industries including petroleum and chemical industries. Consequently, flow measurement becomes a major component in the overall economic success or failure of any given process. Most importantly, accurate flow measurements ensure the safety of the process and for those involved in its success.
    • 3.6: Composition Sensors
      There are many useful analytical tools, such as photometric analysis, electrometric analysis, chromatography, mass spectrometry, thermal conductivity, and various physical property measurements (density and specific gravity), which can be used to determine the composition of mixtures. A wide array of methods to measure composition are available, so it is important to choose the best method given a set of conditions.
    • 3.7: pH and Viscosity Sensors
      pH sensors, while being relatively simple pieces of equipment, have numerous uses. Knowing the pH of a solution is valuable to an analytical chemist attempting to determine the contents of an unknown solution, as well as a farmer trying to determine the appropriate applications to his fields and many people in between. In industry pH sensors can be used as a simple way to monitor reactions involving acids or bases as either a reactant or product of a chemical process.
    • 3.8: Miscellaneous Sensors
      This page is a summary of different sensors not as commonly used as others in industry. This page details the methods of operation, industrial uses, and other relevant information about the sensors.
    • 3.9: Valves - Types, Kinds, and Selection
      Control valves are imperative elements in any system where fluid flow must be monitored and manipulated. Selection of the proper valve involves a thorough knowledge of the process for which it will be used. Involved in selecting the proper valve is not only which type of valve to use, but the material of which it is made and the size it must be to perform its designated task.
    • 3.10: Valves - Modeling Dynamics
      In the following sections we briefly define the various variables and equations involved in modeling valves. The purpose of the following sections is to give you an overview of the equations required to model the valves for a particular system. Example problems at the end of the article have been provided to aid in the qualitative and quantitative understanding of how valves are modeled for chemical engineering processes.

    This page titled 3: Sensors and Actuators is shared under a CC BY 3.0 license and was authored, remixed, and/or curated by Peter Woolf et al. via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.