Tag: instrumentation
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Basic Elements of an Electronic Instrument
An electronic instrument is made up of the following key elements: Transducer This is the first sensing element and is needed only when measuring a non-electrical quantity such as pressure or temperature. Its task is to convert the non-electrical physical quantity into an electrical signal. An example of a transducer is a thermocouple for sensing…
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How Synchros are used as Position Transducers
Let’s consider the transformer in Figure 1.0 whose secondary winding can be rotated with the respect to the primary winding. At an angle ϴ, the output voltage will be given by: Vo = KVicosϴ where K is a constant The output amplitude is dependent on the angle, and the signal can be in phase or…
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Electrical vs. Electronic Instruments
Despite the fact that both electrical and electronic instruments measure electrical quantities like voltage and current, they differ from each other in terms of the built-in features; for example, purely electrical instruments don’t possess any in-built amplifying device to increase the amplitude of the quantity being measured whereas electronic instruments typically incorporate an amplifier. DC…
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The Principle of Piezoelectric Sensing
The piezoelectric transduction is based on the conversion of mechanical vibrations into electrical signals and vice versa. The piezoelectric effect involves the generation of electric charge by a material when subjected to a mechanical deformation. The redistribution of electrical charges in the piezoelectric material causes variations of the electric field inside the material. The reverse…
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Gamma Spectroscopy Measurement Technique
Gamma spectroscopy is a radiochemistry measurement technique that determines the energy and count rate of gamma rays emitted by radioactive substances. A detailed analysis of gamma ray energy spectrum is used to determine the identity and quantity of gamma emitters present in a material. The apparatus used in gamma spectroscopy includes a detector, a pulse…
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Passive vs. Active Sensors
Sensors are normally used to convert physical variables like pressure to signal variables. Sensors are also often termed to as transducers since they are devices that convert input energy of one form into output energy of another form. Sensors can be classified into two broad classes depending on how they interact with the environment they…
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Manipulating Devices & Actuators in Process Instrumentation
The function of the manipulating device is to influence the process variable. Its main purpose is to regulate a mass or energy flow. Mass flows can be either in gaseous or liquid state e.g. steam, natural gas, fuel oil, etc. The energy flows typically take the form of electrical energy. The energy supply can be…
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Designing a System to Measure & Display a Shaft Rotation Speed
We would like to design a system to measure and display the rotational speed of a shaft. To accomplish this, we shall use a number of integrated circuits (ICs) to create the desired functionality of this system. A simple technique to measure the speed is to count the number of shaft rotations during a given…
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What is a Microsyn Transducer?
This is a variable-reluctance transducer used to detect small motions, giving output signals as low as 0.01° of changes in angles. The figure below shows an example of Microsyn: In the Microsyn transducer above, the coils are connected in such a way that at the null position of the rotary element, the voltages in coils…
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Steam-heated Reboiler Control System
When steam-heated reboilers are used in distillation columns and the heating medium is steam, a flow control loop for the steam will typically be incorporated. The control valve can then be placed either in the steam or condensate line. Steam pressure compensation is always recommended in these cases, and the controls are illustrated in the…