Tema 1: Introducción a Sistemas de Instrumentación PDF

# Objetivos y bibliografía del bloque 1 - Introducir y describir los elementos principales de los sistemas de instrumentación y medida. - Analizar las características estáticas y dinámicas de un sensor y conocer su funcionamiento. - Enumerar las principales maneras de acondicionar las señales. - De...

# Objetivos y bibliografía del bloque 1 - Introducir y describir los elementos principales de los sistemas de instrumentación y medida. - Analizar las características estáticas y dinámicas de un sensor y conocer su funcionamiento. - Enumerar las principales maneras de acondicionar las señales. - Describir brevemente los tipos principales de convertidores a digital (ADC) y digital-analógico (DAC). ## Bibliografía - Alan S. Morris. “Measurement & Instrumentation Principles". Butterworth Heinemann, Chapters 1, 2, 3, 5, 7, 8 y 11. # Índice 1. Sistemas de instrumentación 2. Sensores y tipos de sensores # 1. Sistemas de instrumentación The image shows a yellow square, labelled "Sistema de medida," with arrows pointing in and out, indicating flows of information. Inside the square, the following text is printed: - Magnitud física (p, T, F, ...) - Visualización - Almacenamiento - Transmisión The image displays a yellow square with arrows pointing towards it from the bottom and out from the top. The square is labeled "SISTEMA DE MEDIDA." The arrows pointing towards the square represent the flow of physical information or data into the system. They may include measurements such as pressure (p), temperature (T), force (F), and other relevant parameters. The flow of information into the system is indicated as (p, T, F, ...). The arrows pointing out from the top are labeled: - Visualización - Almacenamiento - Transmisión These three arrows represent the flow of information out from the system, displaying the measured data and possibly allowing storage or communication to other systems. The image suggests that the information about a physical quantity measured by a system is processed and then transmitted, stored or displayed. # Medida ## Medida Determining the quantitative value of a characteristic or physical quantity. In practice, measurement involves converting an observation of a physical quantity into a domain where a person or machine can determine its value or magnitude. ## Unidades de medida Units are used to quantify and combine different measurements. Early units were used to exchange goods and materials, such as the length of an arm, an inch, a foot, etc. Over time, the accuracy and precision of measurement units improved significantly. The internationally accepted or standard measurement systems allow for the measurement of a wide range of physical quantities. These systems are constantly being refined and improved through scientific research. ## Medida: Comparación The image shows a wooden structure, featuring ropes, pulleys, and a cotton ball. This structure likely acts as a balance scale, where the weight of the cotton ball is compared against known weights. ## Medida: De la artesanía... The image consists of different human body parts, with lines indicating measurement units. The image demonstrates early methods of measurement, using parts of the human body. The image illustrates the following units: - 1 PALMO (palm) - 1 PIE (foot) - 1 CODO (elbow to fingertip) - 1 YARDA (distance from the tip of the nose to the end of the outstretched arm) - 1 DEDO (finger) ## Medida: ... a la globalización. The image depicts a historical balance scale, an electronic scale, and an analytical scale. This sequence of instruments demonstrates the progression of measurement technology from traditional scales to modern electronic and analytical instruments. ## De la interfaz electrónica... The image is a screen shot from a computer program. The program displays information about data being recorded from an analog input. The program appears to be a data acquisition software package, with visual representation of the recorded data. ## Al todo conectado con todo The image depicts a map of a city with several icons. Each icon represents a different type of sensor with corresponding data being collected. The following sensors are depicted on the map: - Air pollution: monitoring air quality. - Forest fire detection: detecting and preventing forest fires. - Wine Quality Enhancing: controlling wine quality parameters. - Offspring care: monitoring conditions for young animals. - Sportsmen Care: monitoring athletes' vital signs during training and competitions. - Structural health: monitoring structural integrity. - Smartphones detection: detecting smartphones and other Bluetooth-enabled devices. - Perimeter Access Control: restricting access to designated areas. - Radiation Levels: measuring radiation levels. - Electromagnetic Levels: monitoring electromagnetic fields. - Traffic Congestion: monitoring traffic flow. # Unidades de medida ## Sistema internacional de unidades This system is used worldwide and standardizes measurements. ### Fundamental Units The following table contains a list of base units in the International System of Units: | Quantity | Standard Unit | |---|---| | Length | meter | | Mass | kilogram | | Time | second | | Electric current | ampere | | Temperature | kelvin | | Luminous intensity | candela | | Matter | mole | ### Supplementary Units | Quantity | Standard unit | |---|---| # Unidades de medida ## The document explains the definition and recent changes in the system of units. ### Definition of standard units - **Kilogram**: continues to be the standard unit of mass but its value will be determined by fixing the value of Planck's constant *h* to exactly 6.62606 x 10^-34 m². kg/s. - **Ampere**: continues to be the standard unit of electric current but its value will be determined by fixing the numerical value of the elementary charge *e* to exactly 1.60217 x 10^-19 s.A. - **Kelvin**: continues to be the standard unit of thermodynamic temperature but its value will be determined by fixing the numerical value of the Boltzmann constant *k* to exactly 1.3806X x 10^-23 J/K. - **Mole**: continues to be the standard unit of the amount of substance (a specified elementary entity, e.g., atom, molecule, ion, electron, or a specified group of particles) but its value will be determined by fixing the numerical value of Avogadro's constant *N_A* to exactly 6.02214 X 10²³ mol^-1. ### Units redefined in 2018 - **Second**: The unit of time. Its value is determined by fixing the numerical value of the unperturbed ground state hyperfine transition frequency of the cesium 133 atom in its ground state to 9,192,631,770 Hz. - **Meter**: The unit of length. Its value is determined by fixing the numerical value of the speed of light in a vacuum *c* to exactly 299,792,458 m/s. - **Candela**: The unit of luminous intensity. Its value is determined by fixing the numerical value of the luminous efficacy of monochromatic radiation of frequency 540 x 10¹² Hz, denoted *K_cd*, to exactly 683 lm W^-1, which means the luminous intensity of a light source that emits monochromatic radiation at frequency 540 x 10¹² Hz with radiant power of 1/683 watt in a given direction. # Tipos de sensores ## Resistivos - **Termistores o resistencias sensibles a la temperatura**: These can be NTC or PTC. - **NTC(negative temperature coefficient):** Resistance decreases with increasing temperature because more electrons are freed from atoms, particularly in semiconducting materials. - **PTC(positive temperature coefficient):** Resistance increases with increasing temperature due to increased molecular vibration and higher collision frequency. - **Light dependent resistors (LDR or fotoresistores):** - This sensor's resistance varies based on the intensity of light falling on it. - **Example:** cadmium sulfide. - In the absence of light, the concentration of free charge carriers is minimal, leading to high resistance. In low light conditions, a small current called the dark current flows due to residual free charge carriers. When light illuminates the material, more charge carriers get excited causing a lower resistance. The LDR exhibits maximum sensitivity toward red light, around 680nm. It's less effective at light below 400nm or above 850nm. - **Force or pressure sensors (FSR - Force Sensitive Resistors):** - When pressure is applied to a conductor, it can change its dimension and shape. This alters the resistance of the conductor, which can be utilized to measure force or pressure. - **Example:** Piezoresistive effect. - Typically, increased force will result in greater displacement and, therefore, higher resistance. In certain semiconductors, pressure changes cause variations in resistivity, known as the *piezoresistive effect*. - Strain gauges are based on this *piezoresistive* effect and often employ a bridge circuit configuration. - **Displacement sensors:** - They are used to measure small distances, often with a potentiometer. ## Inductivos - **Inductance varies with the magnetic field**: This principle serves as the foundation for detecting metals. - **Based on inductance (L) or mutual inductance (M) changes**: - **Displacement:** The core within an inductor moves relative to the coil, modifying inductance. - **Linear variable differential transformer (LVDT):** - It's used to measure position, displacement, force, or acceleration. It comprises multiple coils wound around a core. When a force pushes the core inside the coil, it alters the inductance of the coils. By measuring the change in inductance, the system can determine the magnitude and direction of the force applied. - **Eddy Current sensors**: - It utilizes a coil with a fixed core. The coil is powered by an alternating current, creating a magnetic field. If a conductor passes near the coil, eddy currents are induced in the conductor, producing a secondary magnetic field that opposes the original field. This opposition causes the impedance of the coil to change, which can be measured. The change in impedance can then be correlated to the attributes of the conductor, including its distance from the coil, thickness, conductivity, or other factors. ## Capacitivos - **Capacitance of a conductor is defined as C = ε₀ ε_r (F)**, where ε₀ is the permittivity of free space, ε_r is the permittivity of the dielectric material between the conductors, F is a geometrical factor determined by the physical dimensions of the conductors. - **Based on variations in the geometrical factor, F, or dielectric material permittivity, ε_r:** - **Temperature** changes can affect a material's permittivity (ε_r). - **Level:** Measuring the dielectric material's changes, usually liquid level. - **Concentration**: Changes in the substance's permittivity can indicate concentration levels. - **Displacement or contact**: These sensors use the movement of a conductor relative to other conductors, modifying the capacitance of the system. - **Example:** Displacement sensors. ## Piezoeléctricos - Some materials exhibit a change in their electrical properties (voltage) when subjected to mechanical forces. - Applied force creates a linear relationship between the force and the electrical charge. This linearity holds true across a wide range of voltages. - Quartz is a natural piezoelectric material. - Often used in accelerometers, among other applications. ## Termoeléctricos - The Seebeck effect: - Conversion of temperature changes into voltage variations. - Different materials have differing charge carrier energy levels. When two distinct materials are connected, charge carriers move from the higher energy level to the lower energy level. This movement creates a voltage difference between the two materials. - A thermocouple is created by joining two dissimilar metals at two junctions, one at a specific temperature (usually 0°C) and the other at the temperature to be measured. The two junctions are electrically connected, creating a circuit. The temperature difference between the two junctions drives the flow of charge carriers, resulting in a voltage that is proportional to the temperature difference. ## Thermocouples - Thermocouples are an important component in various fields, including temperature control systems, industrial furnaces, and research laboratories. - They have some advantages: - Cost-effectiveness - Wide temperature measurement range - However, thermocouples also have drawbacks: - They only measure temperature differences and require a reference temperature which might introduce errors if not calibrated properly. - Sensitive to external factors (e.g. Electromagnetic interference, vibration, humidity). - Thermocouples, despite their limitations, are a valuable tool for measuring temperature. # Tipos de sensores: examples The document has images of sensors from a real truck made by Mercedes-Benz. These sensors are involved in the truck's operation. The document also includes a brainstorming activity about sensors. Choose a sensor that you are curious about and research it. Here are some examples of sensors: - Optical sensor - Ultrasonics sensor - Radiation ionization sensor - Quantum sensors - Fiber optic sensors and FBGs (Fiber Bragg Grating). - Magnetic sensor - Pyroelectric sensor - Bimetallic strip sensor - Strain gauge - Or any other sensor you might be interested in. Finally, the document includes another image of a city scene illustrating how sensors can collect data from various sources.