Tag: instrumentation and control
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Process Control System Design for a Distillation Unit
The aim of a typical control system is to force a given set of process variables to act in some desired and prescribed way by either fulfilling some requirements of the time or frequency domain or achieving the best performances as expressed by an optimization index. The scope of the control tasks varies widely. The…
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Limit Switches vs. Proximity Sensors
An object can be used to activate a switch directly, producing an ON or OFF signal to indicate the presence of that particular object, alternatively we can use the presence of a nearby object to activate a sensor giving a signal which is either ON or OFF. A limit switch is a mechanical switch in…
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Standard Process Signals for Industrial Instrumentation
Industrial measurement and control processes employ standard process signals that are used throughout all the industries. For instance, one of the most popular forms of signal transmission in modern industrial instrumentation systems is the 4-20 mA DC standard. The signal standards employed in industrial instrumentation are unique. Processes are referred to or measured as 0%…
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How the Wiegand Effect is used in Sensing Instruments
The Concept behind Wiegand Effect Based Sensors The Wiegand effect technology employs the unique magnetic properties of specially processed, small-diameter ferromagnetic wire. By causing the magnetic field of this wire to abruptly reverse, a sharp, uniform voltage is generated. This pulse is referred to as a Wiegand pulse. Sensors employing this effect need only…
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Piezoelectric Accelerometer: Principle of Operation & Applications
An accelerometer is a sensor that is designed to measure acceleration or rate of change of speed due to motion, vibration e.g. from rotating equipment and impact events such as the deployment of an automobile airbag. Accelerometers are usually mechanically attached or bonded to an object or structure for which acceleration is to be measured.…
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The USB-6009 Data Acquisition Card Features
The USB-6009 is a small external data acquisition and control device manufactured by National Instruments that is normally connected to a computer through a USB port. It is used in applications such as simple data logging, academic lab experiments and portable measurements. This device has analogue to digital (A/D) conversion capabilities as well as digital…
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Vision Sensors: Features, Concepts & Applications in Manufacturing
Vision Sensors A vision sensor is basically a TV camera connected to a computer, usually a PC. Special vision software analyzes the video image and makes specific recommendation to the work area. Vision systems require computing power to process thousands of pixels of information continuously in order to arrive at a go/no-go decision about what…
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How Cascade Control System Enhances Dynamic Response to Load Changes
The major limitation of a conventional feedback control system is that the correction for disturbances does not start until the process output deviates from the setpoint. Feedforward control provides big improvements in processes with large time constraints or time delays. But, feedforward control requires that the disturbances be measured explicitly and a model must be…
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Cable Screens: Types & Connections
Electromagnetic Compatibility (EMC) is one of the key factors of consideration in the design, construction, manufacture and installation of electrical and electronic equipment and systems. Electrical equipment must be designed not only to meet a functional technical performance specification but due consideration must also be given to the interaction the equipment has with the electromagnetic…
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Instrumentation Systems Installation: Precautions to Take
Analog systems are normally based on low voltages and as a result, they are vulnerable to electrical noise. In most plants, a PLC may be controlling 415 V high power motors at 100 A, and at the same time, reading thermocouple signals of a few mA. Great care must therefore be taken to avoid interference…