Tag: instrumentation
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What are PLC-Based Water Treatment Plants?
Most of the water treatment plants in the previous decade were manually operated. However, they were automated to a certain degree using relays or electrical control panels but the system was not reliable and required a lot of space. In … Read more
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Analog Proportional Controller
An analog controller typically employs op-amps to provide the necessary gain and signal processing. Let’s consider the flow control system below: Figure: Flow control system In the system above, the controller’s function is to maintain the flow of a liquid … Read more
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Electric Solenoid Actuator – Features & Operation
A typical electric solenoid actuator consists of a coil, armature, spring, and stem. This is illustrated in the figure below: Figure: Electric solenoid actuator The coil is connected to an external current supply. The spring rests on the armature to … Read more
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Pressure Control Valve Operation
A pressure control valve is a spring-loaded valve that is capable of maintaining a constant pressure in a system regardless of the flow rate. This is important, since most pumps e.g. gear pumps are constant-displacement types – a constant volume … Read more
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Key Factors to Consider in Selection of Valves
Valves are the final element in a control loop, and are critical in providing the correct flow. The valve, usually operates in very harsh conditions, and is one of the most costly elements in the process control system. Their … Read more
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Features and Applications of Instrument Transformers
Instrument transformers are used in the measurement of voltage, current, energy, and power in ac circuits. The main reasons why instrument transformers are employed in measurements are: To extend (multiply) the range of the measuring instrument. To isolate the measuring … Read more
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The Principle of Operation of a Vortex Flowmeter
If a bluff (non-streamlined) body is placed in a flow, vortices detach themselves at regular intervals from the downstream side as illustrated in the diagram below: Figure: Vortex shedding flowmeter In flow measurement the vortex shedding frequency is usually a … Read more
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The Principle of an Optical Pyrometer Temperature Sensor
A heated object emits electromagnetic radiation. At temperatures below approximately 400 °C this radiation can be felt as heat. As the temperature rises, the object starts to emit visible radiation passing from red through yellow to white. Intuitively we can … Read more
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Types of Ultrasonic Non-Destructive Testing (NDT) Techniques
The technology of ultrasonic testing has been used by production and industry since the development of the radio engineering process. The effect and device of the technology are that ultrasonic waves of acoustic type do not change the rectilinear trajectory … Read more
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The Principle of Operation of Optical Encoders
An encoder is a device that provides a digital output as a result of an angular or linear displacement. The position encoders can be grouped into two categories: Incremental encoders, which detect changes in displacement from some datum position. Absolute … Read more